ORCID Profile
0000-0003-1528-9479
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Publisher: AIP Publishing
Date: 09-1995
DOI: 10.1063/1.359930
Abstract: A very significant Zn evaporation from nongrowing AlxGa1−xAs surface during a post-δ-doping purge step was observed in growth of Zn δ-doped AlxGa1−xAs (x& .65) by low pressure metal organic vapor phase epitaxy using dimethylzinc as a doping precursor. A δ-doping sequence different from the normal ‘‘purge-doping-purge’’ is therefore proposed to minimize the Zn evaporation. Using this δ-doping sequence, the dopant memory effect was investigated and the best hole profile of Zn δ-doped GaAs (Al0.35Ga0.65As) was obtained, having a full width at half-maximum of 7.0 nm for a peak concentration of 1.1×1020 cm−3 (13 nm for 4.8×1018 cm−3). It was found that the growth temperature significantly influences the hole concentration of Zn δ-doped GaAs and the hole concentration decreases and the hole profile width increases with increasing Al content of Zn δ-doped AlxGa1−xAs.
Publisher: American Physical Society (APS)
Date: 05-03-2010
Publisher: AIP Publishing
Date: 30-12-1996
DOI: 10.1063/1.116991
Abstract: We have optimized growth conditions of metal organic vapor phase epitaxy (MOVPE) in order to grow Si and C δ-doped nipi doping superlattices in GaAs. Trimethylaluminium (TMAl) and silane (SiH4) were used as p-type and n-type doping precursors, respectively. We report that at 630 °C, full compensation of free electrons and holes can be obtained in the MOVPE-grown Si and C δ-doped nipi doping superlattices over a very wide range of the sheet carrier densities (1012–1013 cm−2) by choosing proper TMAl flow rate and Si δ-doping time or SiH4 flow rate. The experimental results on electrical and optical characterization of Si and C δ-doped nipi doping superlattices in GaAs with 150 Å thick undoped spacer layers are presented.
Publisher: Springer Science and Business Media LLC
Date: 11-03-2016
DOI: 10.1038/LSA.2016.46
Publisher: IEEE
Date: 12-2012
Publisher: IEEE
Date: 12-2012
Publisher: AIP Publishing
Date: 08-05-2006
DOI: 10.1063/1.2203333
Abstract: We report the experimental results of tuning the emission wavelength of InAs∕InP quantum dots (QDs) by varying either the GaAs interlayer thickness or the indium composition of the InxGa1−xAs interlayer. The InAs QDs are grown on lattice-matched GaInAsP or InP buffers and are capped with an InP layer. As∕P exchange is prominent when the QDs are grown on an InP buffer. A model is developed which considers the As∕P exchange, gallium interdiffusion, strain, and barrier height. Our theoretical and experimental results show that gallium interdiffusion and the As∕P exchange reaction are mainly responsible for the observed shifts in the QD emission wavelength. The model shows that gallium interdiffusion from the interlayer to the InAs QDs grown on a GaInAsP buffer can be utilized to selectively tune the InAs QD emission wavelength over a wide range.
Publisher: IEEE
Date: 12-2012
Publisher: American Chemical Society (ACS)
Date: 18-03-2011
DOI: 10.1021/NL104330H
Publisher: IOP Publishing
Date: 29-07-2014
Publisher: AIP Publishing
Date: 22-11-1999
DOI: 10.1063/1.125344
Abstract: Single Al0.5Ga0.5As/GaAs V-groove quantum wires (QWR) modified by selective implantation and rapid thermally annealing were investigated by spatially resolved microphotoluminescence (micro-PL). The PL from the necking region was clearly observed at room temperature. Optical properties of QWR and the adjacent quantum well structures were strongly degraded by the implantation. The recovery properties of the PL signals from all the structures were dependent on the implantation dose. A critical dose of 1×1013 cm−2 was found for the selective implantation, over which the PL from the necking region could not be recovered. Also the blueshifts of QWR and the necking-region PL peaks were observed for all the annealed s les. This blueshift is caused by the interface intermixing, which is very useful to increase the confinement of carriers in QWR region for optoelectronic device applications.
Publisher: IEEE
Date: 10-2007
Publisher: IOP Publishing
Date: 06-07-2007
Publisher: AIP Publishing
Date: 13-01-2014
DOI: 10.1063/1.4859915
Abstract: Droplet epitaxy is an important method to produce epitaxial semiconductor quantum dots (QDs). Droplet epitaxy of III-V QDs comprises group III elemental droplet deposition and the droplet crystallization through the introduction of group V elements. Here, we report that, in the droplet epitaxy of InAs/GaAs(001) QDs using metal-organic chemical vapor deposition, significant elemental diffusion from the substrate to In droplets occurs, resulting in the formation of In(Ga)As crystals, before As flux is provided. The supply of As flux suppresses the further elemental diffusion from the substrate and promotes surface migration, leading to large island formation with a low island density.
Publisher: AIP Publishing
Date: 20-05-2013
DOI: 10.1063/1.4807597
Abstract: In this study, Pd was used as catalyst to grow one-dimensional InAs nanostructures on GaAs (111)B substrates in order to explore the growth mechanism and the effect of non-gold catalysts in growing epitaxial III-V nanostructures. With detailed morphological, structural, and chemical characterizations using electron microscopy, coupled with analysis of the Pd-In binary phase diagram, it was found that size of Pd nanoparticles plays a key role in determining the growth mechanism of one-dimensional InAs nanostructures.
Publisher: Elsevier BV
Date: 07-1998
Publisher: IEEE
Date: 12-2012
Publisher: IEEE
Date: 12-2012
Publisher: IEEE
Date: 09-2013
Publisher: IEEE
Date: 12-2012
Publisher: IEEE
Date: 08-2018
Publisher: IEEE
Date: 10-2009
Publisher: American Chemical Society (ACS)
Date: 29-07-2016
DOI: 10.1021/ACS.NANOLETT.6B01973
Abstract: We present the design and room-temperature lasing characteristics of single nanowires containing coaxial GaAs/AlGaAs multiple quantum well (MQW) active regions. The TE01 mode, which has a doughnut-shaped intensity profile and is polarized predominantly in-plane to the MQWs, is predicted to lase in these nanowire heterostructures and is thus chosen for the cavity design. Through gain and loss calculations, we determine the nanowire dimensions required to minimize loss for the TE01 mode and determine the optimal thickness and number of QWs for minimizing the threshold sheet carrier density. In particular, we show that there is a limit to the minimum and maximum number of QWs that are required for room-temperature lasing. Based on our design, we grew nanowires of a suitable diameter containing eight uniform coaxial GaAs/AlGaAs MQWs. Lasing was observed at room temperature from optically pumped single nanowires and was verified to be from TE01 mode by polarization measurements. The GaAs MQW nanowire lasers have a threshold fluence that is a factor of 2 lower than that previously demonstrated for room-temperature GaAs nanowire lasers.
Publisher: American Physical Society (APS)
Date: 27-12-2011
Publisher: AIP Publishing
Date: 17-04-2006
DOI: 10.1063/1.2193433
Abstract: Experimental results on spontaneous emission rates from InGaAs quantum dot lasers that can be explained theoretically by considering the influence of nonradiative mixed state recombinations in the quantum dot-wetting layer system are presented. Our model qualitatively explains the experimental results such as an increase in the threshold current density, temperature stability, and a narrower gain spectrum due to doping the quantum dot active region with the acceptors. Our model also predicts that moderate acceptor concentrations can improve the laser performance at higher carrier injection densities but high acceptor concentrations deteriorate the laser performance due to the nonradiative Auger recombination that counteracts the benefits of increased spontaneous emission rates.
Publisher: AIP Publishing
Date: 06-1999
DOI: 10.1063/1.370616
Abstract: The effect of ion implantation-induced interdiffusion on the resonant wavelength of GaAs/AlxOy distributed Bragg reflectors is investigated. As interdiffusion becomes stronger, the resonant wavelength is seen to redshift. Shifts of more than 60 nm could be achieved for center wavelengths around 800 nm. A model is proposed to explain this behavior. This model agrees well with previous lateral oxidation studies.
Publisher: AIP Publishing
Date: 04-2010
DOI: 10.1063/1.3368598
Abstract: A new optical front-end compensation technique to suppress the unwanted, spurious signal in photoreflectance (PR) spectroscopy is developed. In this approach an optical compensation signal, which is litude-matched to and in antiphase to the spurious signal, is introduced and directed to the photodetector. The combination of the compensation signal and the spurious signal results in a dc output from the photodetector which is thereafter suppressed by the lock-in lifier, leaving only the true PR signal to be recovered and lified. A high spurious signal suppression efficiency is demonstrated and the advantages of the technique are discussed.
Publisher: IOP Publishing
Date: 21-02-2017
Abstract: With the recent advances in nanowire (NW) growth and fabrication, there has been rapid development and application of GaAs NWs in optoelectronics. It is also of importance to study the radiation tolerance of optoelectronic nano-devices for atomic energy and space-based applications. Here, photoluminescence (PL) and time-resolved photoluminescence measurements were carried out on GaAs/AlGaAs core/shell NWs at room temperature before and after 1 MeV proton irradiation with fluences ranging from 1.0 × 10
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5NR04129E
Abstract: A simple nanowire growth model is established to explain the observed growth trend of ternary InGaAs nanowires, in particular, their growth rate and composition.
Publisher: American Chemical Society (ACS)
Date: 05-09-2013
DOI: 10.1021/NN403390T
Abstract: Semiconductor nanowires have proven a versatile platform for the realization of novel structures unachievable by traditional planar epitaxy techniques. Among these, the periodic arrangement of twin planes to form twinning superlattice structures has generated particular interest. Here we demonstrate twinning superlattice formation in GaAs nanowires and investigate the diameter dependence of both morphology and twin plane spacing. An approximately linear relationship is found between plane spacing and nanowire diameter, which contrasts with previous results reported for both InP and GaP. Through modeling, we relate this to both the higher twin plane surface energy of GaAs coupled with the lower supersaturation relevant to Au seeded GaAs nanowire growth. Understanding and modeling the mechanism of twinning superlattice formation in III-V nanowires not only provides fundamental insight into the growth process, but also opens the door to the possibility of tailoring twin spacing for various electronic and mechanical applications.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5NR06996C
Abstract: Single core–multishell nanowires with a radial quantum well are probed by micro-photoluminescence spectroscopy revealing low disorder in both the core and quantum well.
Publisher: IEEE
Date: 05-2013
Publisher: AIP Publishing
Date: 04-2009
DOI: 10.1063/1.3103265
Abstract: The movement of Au catalysts during growth of InAs on GaAs nanowires has been carefully investigated by transmission electron microscopy. It has been found that Au catalysts preferentially stay on {112}B GaAs sidewalls. Since a {112} surface is composed of a {111} facet and a {002} facet and since {111} facets are polar facets for the zinc-blende structure, this crystallographic preference is attributed to the different interface energies caused by the different polar facets. We anticipate that these observations will be useful for the design of nanowire heterostructure based devices.
Publisher: AIP Publishing
Date: 11-05-2009
DOI: 10.1063/1.3138137
Abstract: Simple photolithographic techniques are used to fabricate single InP nanowire devices with back-to-back Schottky barriers. Direct imaging of the photoresponse shows that the active regions of the device are spatially localized near the reverse-biased Schottky barrier. By tuning the laser excitation energy from below to well above the energy gap, photocurrent spectroscopy can illuminate the zincblende or wurtzite nature of the nanowire device even at room temperature.
Publisher: Wiley
Date: 23-10-2018
Publisher: AIP Publishing
Date: 28-08-2000
DOI: 10.1063/1.1290267
Abstract: We present direct experimental evidence for a field assisted component in images acquired using the gaseous secondary electron detector (GSED) employed in environmental scanning electron microscopes. Enhanced secondary electron (SE) emission was observed in GSED images of epitaxial GaN bombarded with MeV He ions. The increase in SE emission is attributed to an electric field generated by electrons trapped at defects produced by ion implantation. The presence of nonradiative recombination centers and of trapped charge in implanted GaN was established by cathodoluminescence spectroscopy and energy dispersive x-ray spectrometry. The field assisted SE component is distinguishable from the “normal” GSED signal by characteristic pressure and temperature dependencies. The presented results demonstrate the utility of the GSED for imaging charge trap distributions in semiconductors.
Publisher: IEEE
Date: 08-2010
Publisher: American Physical Society (APS)
Date: 18-11-2013
Publisher: IEEE
Date: 12-2012
Publisher: IEEE
Date: 2005
Publisher: IEEE
Date: 2005
Publisher: American Chemical Society (ACS)
Date: 16-09-2011
DOI: 10.1021/NL202433G
Abstract: The internal electronic structures of single semiconductor nanowires can be resolved using photomodulated Rayleigh scattering spectroscopy. The Rayleigh scattering from semiconductor nanowires is strongly polarization sensitive which allows a nearly background-free method for detecting only the light that is scattered from a single nanowire. While the Rayleigh scattering efficiency from a semiconductor nanowire depends on the dielectric contrast, it is relatively featureless as a function of energy. However, if the nanowire is photomodulated using a second pump laser beam, the internal electronic structure can be resolved with extremely high signal-to-noise and spectral resolution. The photomodulated Rayleigh scattering spectra can be understood theoretically as a first derivative of the scattering efficiency that results from a modulation of the band gap and depends sensitively on the nanowire diameter. Fits to spectral lineshapes provide both the band structure and the diameter of in idual GaAs and InP nanowires under investigation.
Publisher: American Chemical Society (ACS)
Date: 18-07-2016
DOI: 10.1021/ACS.NANOLETT.6B01528
Abstract: Terahertz time-domain spectroscopy (THz-TDS) has emerged as a powerful tool for materials characterization and imaging. A trend toward size reduction, higher component integration, and performance improvement for advanced THz-TDS systems is of increasing interest. The use of single semiconducting nanowires for terahertz (THz) detection is a nascent field that has great potential to realize future highly integrated THz systems. In order to develop such components, optimized material optoelectronic properties and careful device design are necessary. Here, we present antenna-optimized photoconductive detectors based on single InP nanowires with superior properties of high carrier mobility (∼1260 cm(2) V(-1) s(-1)) and low dark current (∼10 pA), which exhibit excellent sensitivity and broadband performance. We demonstrate that these nanowire THz detectors can provide high quality time-domain spectra for materials characterization in a THz-TDS system, a critical step toward future application in advanced THz-TDS system with high spectral and spatial resolution.
Publisher: The Electrochemical Society
Date: 2011
DOI: 10.1149/1.3532767
Publisher: Elsevier BV
Date: 03-1995
Publisher: IOP Publishing
Date: 09-05-2006
Publisher: AIP Publishing
Date: 2001
DOI: 10.1063/1.1337646
Abstract: Cathodoluminescence (CL) spectroscopy shows that even relatively low-dose keV light-ion bombardment (corresponding to the generation of ∼5×1019 vacancies/cm3) of wurtzite GaN results in a dramatic quenching of visible CL emission. Postimplantation annealing at temperatures up to 1050 °C generally causes a partial recovery of measured CL intensities. However, CL depth profiles indicate that, in most cases, such a recovery results from CL emission from virgin GaN, beyond the implanted layer due to a reduction in the extent of light absorption within the implanted layer. In this case, CL emission from the implanted layer remains completely quenched even after such an annealing. These results show that an understanding of the effects of ion bombardment and postimplantation annealing on luminescence generation and light absorption is required for a correct interpretation of luminescence spectra of GaN optically doped by keV ion implantation.
Publisher: IOP Publishing
Date: 09-10-2006
Publisher: American Chemical Society (ACS)
Date: 04-02-2010
DOI: 10.1021/NL903688V
Abstract: Controlling the crystallographic phase purity of III-V nanowires is notoriously difficult, yet this is essential for future nanowire devices. Reported methods for controlling nanowire phase require dopant addition, or a restricted choice of nanowire diameter, and only rarely yield a pure phase. Here we demonstrate that phase-perfect nanowires, of arbitrary diameter, can be achieved simply by tailoring basic growth parameters: temperature and V/III ratio. Phase purity is achieved without sacrificing important specifications of diameter and dopant levels. Pure zinc blende nanowires, free of twin defects, were achieved using a low growth temperature coupled with a high V/III ratio. Conversely, a high growth temperature coupled with a low V/III ratio produced pure wurtzite nanowires free of stacking faults. We present a comprehensive nucleation model to explain the formation of these markedly different crystal phases under these growth conditions. Critical to achieving phase purity are changes in surface energy of the nanowire side facets, which in turn are controlled by the basic growth parameters of temperature and V/III ratio. This ability to tune crystal structure between twin-free zinc blende and stacking-fault-free wurtzite not only will enhance the performance of nanowire devices but also opens new possibilities for engineering nanowire devices, without restrictions on nanowire diameters or doping.
Publisher: AIP Publishing
Date: 11-03-1996
DOI: 10.1063/1.115679
Abstract: Ion implantation damage and the regrowth process during thermal annealing of 2 MeV As-ion-implanted GaAs were studied by transmission electron microscopy. With low-temperature annealing, a high denisty of stacking faults was formed during the recrystallization process, but they were rarely observed with high-temperature annealing. At intermediate temperatures, a much lower denisty of stacking faults was generated at the upper interface between the buried amorphous layer and the crystal than that at the lower interface, where a higher concentration of as-implanted arsenic exists. Based on the observed experimental results, an atomic model is proposed to explain the formation of stacking faults induced by As clusters.
Publisher: American Chemical Society (ACS)
Date: 08-08-2022
Publisher: The Optical Society
Date: 15-03-2002
DOI: 10.1364/OL.27.000436
Abstract: We report passive mode-locking experiments with a novel self-doubling laser crystal Yb:YAl(3)(BO(3))(4) (Yb:YAB). The diode-pumped laser was mode locked by an ion-implanted semiconductor saturable absorber mirror. Far off phase matching, soliton mode locking produced pulse widths of 198 fs to 1.4 ps, with up to 660-mW output and optical efficiency of 24% at 1040 nm. The shortest pulses had a peak power of 28 kW with 440-mW average power and 16% efficiency. A few degrees off phase matching, a total of 60 mW of green femtosecond pulses was generated simultaneously. Close to phase matching, the laser produced picosecond pulses and, without infrared output, a total of 270 mW of green output, corresponding to 10% conversion efficiency (absorbed pump to green output).
Publisher: IOP Publishing
Date: 02-04-2007
Publisher: AIP Publishing
Date: 11-02-2002
DOI: 10.1063/1.1448175
Abstract: The deformation behavior of bulk ZnO single crystals is studied by a combination of spherical nanoindentation and atomic force microscopy. Results show that ZnO exhibits plastic deformation for relatively low loads (≳4–13 mN with an ∼4.2 μm radius spherical indenter). Interestingly, the elastic–plastic deformation transition threshold depends on the loading rate, with faster loading resulting, on average, in larger threshold values. Multiple discontinuities (so called “pop-in” events) in force–displacement curves are observed during indentation loading. No discontinuities are observed on unloading. Slip is identified as the major mode of plastic deformation in ZnO, and pop-in events are attributed to the initiation of slip. An analysis of partial load–unload data reveals values of the hardness and Young’s modulus of 5.0±0.1 and 111.2±4.7 GPa, respectively, for a plastic penetration depth of 300 nm. Physical processes determining deformation behavior of ZnO are discussed.
Publisher: IEEE
Date: 12-2012
Publisher: AIP Publishing
Date: 09-1996
DOI: 10.1063/1.363186
Abstract: The nature of ion damage buildup and amorphization in GaAs–AlxGa1−xAs multilayers at liquid-nitrogen temperature is investigated for a variety of compositions and structures using Rutherford backscattering-channeling and cross-sectional transmission electron microscopy techniques. In this multilayer system, damage accumulates preferentially in the GaAs layers however, the presence of AlGaAs enhances the dynamic annealing process in adjacent GaAs regions and thus amorphization is retarded close to the GaAs–AlGaAs interfaces even when such regions suffer maximum collisional displacements. This dynamic annealing in AlGaAs and at GaAs–AlGaAs interfaces is more efficient with increasing Al content however, the dynamic annealing process is not perfect and an amorphous phase may be formed at the interface above a critical defect level or ion dose. Once an amorphous phase is nucleated, amorphization proceeds rapidly into the adjacent AlGaAs. This is explained in terms of the interplay between defect migration and defect trapping at an amorphous–crystalline or GaAs–AlGaAs interface. In addition, enhanced recrystallization of the amorphous GaAs at the interface may occur during heating if an amorphous phase is not formed in the adjacent AlGaAs layer. This is most likely the result of mobile defects injected from the AlGaAs layer during heating.
Publisher: American Chemical Society (ACS)
Date: 16-05-2023
Publisher: AIP Publishing
Date: 31-05-2002
DOI: 10.1063/1.1484244
Abstract: We have used photoluminescence, deep level transient spectroscopy and x-ray photoelectron spectroscopy to investigate the mechanisms of impurity-free disordering in GaAs-based structures using doped spin-on silica layers. We demonstrate that VGa is efficiently converted into arsenic-antisite, AsGa, related defects (EL2-type defects) when the GaAs layer is under compressive stress. We propose that the efficient formation of EL2-type defects reduces the efficiency of impurity-free interdiffusion of GaAs/AlGaAs quantum wells.
Publisher: Elsevier BV
Date: 09-1999
Publisher: AIP Publishing
Date: 09-2008
DOI: 10.1063/1.2969035
Abstract: Photoconductive detectors are convenient devices for detecting pulsed terahertz radiation. We have optimized Fe+ ion-damaged InP materials for photoconductive detector signal to noise performance using dual-energy doses in the range from 2.5×1012 to 1.0×1016 cm−2. Ion implantation allowed the production of semiconducting materials with free-carrier lifetimes between 0.5 and 2.1 ps, which were measured by optical pump terahertz probe spectroscopy. The time resolved photoconductivity of the detector substrates was acquired as a function of time after excitation by 2 nJ pulses from a laser oscillator. These data, when combined with a deconvolution algorithm, provide an excellent spectral response correction to the raw photocurrent signal recorded by the photoconductive detectors.
Publisher: American Chemical Society (ACS)
Date: 13-06-2013
DOI: 10.1021/NL401175T
Abstract: The mechanical behavior of vertically aligned single-crystal GaAs nanowires grown on GaAs(111)B surface was investigated using in situ deformation transmission electron microscopy. Anelasticity was observed in nanowires with small diameters and the anelastic behavior was affected by the crystalline defects in the nanowires. The underlying mechanism for the observed anelasticity is discussed. The finding opens up the prospect of using nanowire materials for nanoscale d ing applications.
Publisher: American Chemical Society (ACS)
Date: 07-12-2018
DOI: 10.1021/ACS.NANOLETT.8B04048
Abstract: Semiconductor nanowires suffer from significant non-radiative surface recombination however, heavy p-type doping has proven to be a viable option to increase the radiative recombination rate and, hence, quantum efficiency of emission, allowing the demonstration of room-temperature lasing. Using a large-scale optical technique, we have studied Zn-doped GaAs nanowires to understand and quantify the effect of doping on growth and lasing properties. We measure the non-radiative recombination rate ( k
Publisher: IOP Publishing
Date: 15-04-2009
Publisher: Trans Tech Publications, Ltd.
Date: 06-2010
DOI: 10.4028/WWW.SCIENTIFIC.NET/KEM.442.398
Abstract: This paper reports the experimental work on the characterization of quantum dot-in-well (DWELL) solar cell grown by metal-organic chemical vapor deposition (MOCVD) without employing any post-growing optimization like antireflection coating and metal grid. The structure of the 10-layer DWELL solar cells is studied by cross-sectional transmission electron microscopy (TEM). Room temperature photoluminescence (PL) spectra show strong quantization at 1178.5 nm with a linewidth of 79.9 nm. External quantum efficiency spectra show enhancement in the spectral response of the photocurrent with respect to the reference quantum dot cell (without DWELL structure). In spite of the reduction in conversion efficiency due to poor collection of current in external circuit compared to reference quantum dot cell it show the improvement in open circuit voltage.
Publisher: IEEE
Date: 09-2013
Publisher: Elsevier BV
Date: 12-1995
Publisher: AIP Publishing
Date: 10-11-2003
DOI: 10.1063/1.1622797
Abstract: A strong influence of ion implantation flux on the accumulation of radiation damage, the so-called dose rate effect, is observed and systematically studied in SiC. 100 keV Si+ ions were implanted into bulk 4H-SiC wafers using different ion fluxes (1.9×1010–4.9×1013 ions/cm2 s) and keeping the implantation dose constant at 5×1014 Si+/cm2. The implants were performed both at room and elevated temperatures, up to 220 °C. Rutherford backscattering spectrometry in the channelling mode using 2 MeV He+ ions was employed to measure ion implantation damage profiles in the s les. For the flux interval used the most, pronounced dynamic annealing effect was detected at 80–160 °C, having an activation energy of 1.3 eV. For ex le, at 100 °C the amount of disordered Si atoms at the projected ion range is reduced by a factor of 4 by decreasing the ion flux from 4.9×1013 to 1.9×1010 ions/cm2 s. The results are discussed in terms of migration and annihilation of intrinsic type defects for both the Si- and C-sublattices. In addition, two regions for the damage accumulation – at the surface and at the damage peak for 100 keV Si+ ions – are observed.
Publisher: Springer Science and Business Media LLC
Date: 08-08-2017
DOI: 10.1038/S41598-017-07970-7
Abstract: Intermediate band solar cells (IBSCs) are conceptual and promising for next generation high efficiency photovoltaic devices, whereas, IB impact on the cell performance is still marginal due to the weak absorption of IB states. Here a rational design of a hybrid structure composed of ZnTe:O/ZnO core-shell nanowires (NWs) with Al bowtie nanoantennas is demonstrated to exhibit strong ability in tuning and enhancing broadband light response. The optimized nanowire dimensions enable absorption enhancement by engineering leaky-mode dielectric resonances. It maximizes the overlap of the absorption spectrum and the optical transitions in ZnTe:O intermediate-band (IB) photovoltaic materials, as verified by the enhanced photoresponse especially for IB states in an in idual nanowire device. Furthermore, by integrating Al bowtie antennas, the enhanced exciton-plasmon coupling enables the notable improvement in the absorption of ZnTe:O/ZnO core-shell single NW, which was demonstrated by the profound enhancement of photoluminescence and resonant Raman scattering. The marriage of dielectric and metallic resonance effects in subwavelength-scale nanowires opens up new avenues for overcoming the poor absorption of sub-gap photons by IB states in ZnTe:O to achieve high-efficiency IBSCs.
Publisher: The Electrochemical Society
Date: 2005
DOI: 10.1149/1.1848293
Publisher: American Chemical Society (ACS)
Date: 21-02-2006
DOI: 10.1021/NL052189O
Abstract: We have synthesized ternary InGaAs nanowires on (111)B GaAs surfaces by metal-organic chemical vapor deposition. Au colloidal nanoparticles were employed to catalyze nanowire growth. We observed the strong influence of nanowire density on nanowire height, tapering, and base shape specific to the nanowires with high In composition. This dependency was attributed to the large difference of diffusion length on (111)B surfaces between In and Ga reaction species, with In being the more mobile species. Energy dispersive X-ray spectroscopy analysis together with high-resolution electron microscopy study of in idual InGaAs nanowires shows large In/Ga compositional variation along the nanowire supporting the present diffusion model. Photoluminescence spectra exhibit a red shift with decreasing nanowire density due to the higher degree of In incorporation in more sparsely distributed InGaAs nanowires.
Publisher: American Physical Society (APS)
Date: 28-02-2001
Publisher: American Chemical Society (ACS)
Date: 14-02-2013
DOI: 10.1021/NL304607V
Abstract: Axially resolved microphotoluminescence mapping of semiconductor nanowires held in an optical tweezers reveals important new experimental information regarding equilibrium trapping points and trapping stability of high aspect ratio nanostructures. In this study, holographic optical tweezers are used to scan trapped InP nanowires along the beam direction with respect to a fixed excitation source and the luminescent properties are recorded. It is observed that nanowires with lengths on the range of 3-15 μm are stably trapped near the tip of the wire with the long segment positioned below the focus in an inverted trapping configuration. Through the use of trap multiplexing we investigate the possibility of improving the axial stability of the trapped nanowires. Our results have important implication for applications of optically assisted nanowire assembly and optical tweezers based scanning probes microscopy.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2022
Publisher: Elsevier BV
Date: 02-1998
Publisher: American Chemical Society (ACS)
Date: 19-09-2012
DOI: 10.1021/NL302767U
Abstract: Using a new technique, transient Rayleigh scattering, we show that measurements from a single GaAs/AlGaAs core-shell semiconductor nanowire provide sensitive and detailed information on the time evolution of the density and temperature of the electrons and holes after photoexcitation by an intense laser pulse. Through band filling, band gap renormalization, and plasma screening, the presence of a dense and hot electron-hole plasma directly influences the real and imaginary parts of the complex index of refraction that in turn affects the spectral dependence of the Rayleigh scattering cross-section in well-defined ways. By measuring this spectral dependence as a function of time, we directly determine the thermodynamically independent density and temperature of the electrons and holes as a function of time after pulsed excitation as the carriers thermalize to the lattice temperature. We successfully model the results by including ambipolar transport, recombination, and cooling through optic and acoustic phonon emission that quantify the hole mobility at ∼68,000 cm(2)/V·s, linear decay constant at 380 ps, bimolecular recombination rate at 4.8 × 10(-9) cm(3)/s and the energy-loss rate of plasma due to optical and acoustic phonon emission.
Publisher: AIP Publishing
Date: 24-05-2010
DOI: 10.1063/1.3436562
Abstract: This paper presents a study on the emission efficiency enhancement of InAsSb nanostructures using a carrier blocking layer. InP is proposed to serve as the carrier blocking layer to suppress the thermal escape of carriers in InAsSb nanostructures and significantly enhance their emission efficiency at high temperature (good photoluminescence signal even at 330 K). However, this leads to a blueshift in their emission wavelength due to the significantly increased quantum confinement of the nanostructures. By inserting a thin InGaAs layer between InP blocking layer and InAsSb nanostructures, longer emission wavelength can be maintained. This provides an approach to achieve InAsSb nanostructures with both good high-temperature optical characteristics and long emission wavelength, which is very useful for fabricating mid-infrared emitters operating at room temperature.
Publisher: American Chemical Society (ACS)
Date: 08-07-2014
DOI: 10.1021/NL500870E
Abstract: The possibility to grow in zincblende (ZB) and/or wurtzite (WZ) crystal phase widens the potential applications of semiconductor nanowires (NWs). This is particularly true in technologically relevant III-V compounds, such as GaAs, InAs, and InP, for which WZ is not available in bulk form. The WZ band structure of many III-V NWs has been widely studied. Yet, transport (that is, carrier effective mass) and spin (that is, carrier g-factor) properties are almost experimentally unknown. We address these issues in a well-characterized material: WZ indium phosphide. The value and anisotropy of the reduced mass (μ exc) and g-factor (g exc) of the band gap exciton are determined by photoluminescence measurements under intense magnetic fields (B, up to 28 T) applied along different crystallographic directions. μ exc is 14% greater in WZ NWs than in a ZB bulk reference and it is 6% greater in a plane containing the WZ ĉ axis than in a plane orthogonal to ĉ. The Zeeman splitting is markedly anisotropic with g exc = |ge| = 1.4 for B⊥ĉ (where ge is the electron g-factor) and g exc = |ge - gh,//| = 3.5 for B//ĉ (where gh,// is the hole g-factor). A noticeable B-induced circular dichroism of the emitted photons is found only for B//ĉ, as expected in WZ-phase materials.
Publisher: IEEE
Date: 09-2017
Publisher: American Physical Society (APS)
Date: 30-06-1997
Publisher: AIP Publishing
Date: 17-04-2002
DOI: 10.1063/1.1467605
Abstract: The influence of ion-beam-produced lattice defects as well as H, B, C, N, O, and Si, introduced by ion implantation, on the luminescence properties of wurtzite GaN is studied by cathodoluminescence spectroscopy. Results indicate that intrinsic lattice defects produced by ion bombardment mainly act as nonradiative recombination centers and do not give rise to the yellow luminescence (YL) of GaN. Experimental data unequivocally shows that C is involved in the defect-impurity complex responsible for YL. In addition, C-related complexes appear to act as efficient nonradiative recombination centers. Implantation of H produces a broad luminescent peak which is slightly blueshifted with respect to the C-related YL band in the case of high excitation densities. The position of this H-related YL peak exhibits a blueshift with increasing excitation density. Based on this experimental data and results reported previously, the chemical origin of the YL band is discussed.
Publisher: SPIE
Date: 25-03-2004
DOI: 10.1117/12.523517
Publisher: IEEE
Date: 10-2007
Publisher: IOP Publishing
Date: 03-08-2012
DOI: 10.1088/0957-4484/23/33/335704
Abstract: A practical bottleneck prohibiting the rapid, confident and damage-free electrical contacting of vapour-liquid-solid grown nanowires arises from the random spatial distribution and variation in quality of the nanowires, and the contact dimensions required. Established techniques such as electron-beam lithography or focused ion-beam deposition have challenges in scaling, damage or complexity that can make a large statistical s le difficult. We present a direct laser-writing technique to allow rapid electrical contacting of nanowires on a large variety of substrates.
Publisher: Springer Science and Business Media LLC
Date: 2013
DOI: 10.1557/OPL.2013.990
Abstract: In this study, Pd thin film is used as catalyst to grow epitaxial InAs nanowires on GaAs(111) B substrate in a metal-organic chemical vapor deposition reactor to explore the growth mechanism and the effects of non-gold catalysts in the growth of III-V epitaxial nanowires. Through detailed morphological, structural and chemical characterization using scanning and transmission electron microscopy, it is found that defect-free zinc-blende structured epitaxial InAs nanowires are grown along the directions with four {111} sidewall facets forming a diamond shaped cross-section. Furthermore, the interface between the nanowire/catalyst is found to be the uncommon {113} planes. It is anticipated that these zinc-blende structured InAs nanowires are grown via the vapor-liquid-solid mechanism. The defect-free nature of these nanowires arises from the non- growth direction and non-{111} nanowire/catalyst interface.
Publisher: SPIE
Date: 07-12-2013
DOI: 10.1117/12.2049016
Publisher: American Chemical Society (ACS)
Date: 21-07-2017
Publisher: IEEE
Date: 10-2011
Publisher: AIP Publishing
Date: 21-01-2013
DOI: 10.1063/1.4789513
Abstract: Graded growth technique is utilized to realize the control over the composition, morphology, and optical properties of self-assembled InAsSb/InGaAs/InP nanostructures. By increasing the initial mole fraction of the Sb precursor during the graded growth of InAsSb, more Sb atoms can be incorporated into the InAsSb nanostructures despite the same Sb mole fraction averaged over the graded growth. This leads to a shape change from dots to dashes/wires for the InAsSb nanostructures. As a result of the composition and morphology change, photoluminescence from the InAsSb nanostructures shows different polarization and temperature characteristics. This work demonstrates a technologically important technique—graded growth, to control the growth and the resultant physical properties of self-assembled semiconductor nanostructures.
Publisher: IEEE
Date: 09-2013
Publisher: AIP Publishing
Date: 05-03-2003
DOI: 10.1063/1.1554761
Abstract: Deep level transient spectroscopy was employed to determine the electrical properties of defects induced in metalorganic chemical-vapor deposition grown n-type and p-type GaAs during proton bombardment. Thermal stability of these defects was investigated and correlation with defects responsible for isolation of GaAs by ion bombardment was discussed. The annealing temperature region (220–250 °C) is similar to proton isolated GaAs below the threshold dose for complete isolation. At least four of the five traps observed in n-type GaAs are not simple interstitial-vacancy pairs. For p-type GaAs we have observed an unknown level with apparent energy of ∼0.64 eV.
Publisher: Elsevier BV
Date: 02-2001
Publisher: AIP Publishing
Date: 27-04-2009
DOI: 10.1063/1.3126443
Abstract: We report on the use of In2O3 nanowires with hexagonal cross section as optical whispering gallery resonators. The single-crystal In2O3 nanowires were fabricated by an in situ thermal oxidation method. Whispering gallery modes (WGMs) in the visible spectral range were directly observed at room temperature. Due to the slight tapering of the nanowires, the energies and orders of the WGMs were modulated when excitations were scanned along the c-axis (length) of the nanowires. The experimental results were explained and fitted well with a plane wave interference model and Cauchy dispersion formula for refractive indices.
Publisher: AIP Publishing
Date: 27-05-2003
DOI: 10.1063/1.1579565
Abstract: Undoped In0.53Ga0.47As epilayers were implanted with 2-MeV Fe+ ions at doses of 1×1015 and 1×1016 cm−2 at room temperature and annealed at temperatures between 500 and 800 °C. Hall-effect measurements show that after annealing, layers with resistivities on the order of 105 Ω/square can be achieved. Carrier lifetimes as short as 300 fs are observed for s les annealed at 500 and 600 °C. For higher annealing temperatures, characteristic times of the optical response are on the order of a few picoseconds.
Publisher: SPIE
Date: 12-06-2001
DOI: 10.1117/12.429438
Publisher: IOP Publishing
Date: 13-07-2012
DOI: 10.1088/0022-3727/45/30/305102
Abstract: In this paper, a staircase plasmonic nano-antenna device is analysed both theoretically and experimentally. The tapered nano-antenna cavity with a grating leads to electric field enhancement factor (EF) as high as 31 close to 830 nm. The integration of a metallic grating aids the coupling of light coming from the vertical direction to the nano-antenna, increasing the electric field in the nano-antenna by a factor of 3. The smallest air gap width between the metallic regions of the fabricated nano-antenna is about 35 nm, fabricated using focused ion beam system. The small air gaps in the nano-antennas can generate very high intensity electric fields which can be used in applications in biological sensing and imaging, nanoparticle manipulations and enhancement of nonlinear effects. In this paper, to experimentally demonstrate that with the integration of a well designed grating and reflectors, the resonance inside the nano-antenna cavity is increased significantly, we exploit one application of this device: the enhancement of surface enhanced Raman scattering (SERS). The present structure can lead to SERS EFs above 1 million.
Publisher: AIP Publishing
Date: 27-09-2010
DOI: 10.1063/1.3496456
Abstract: Third generation biosensor based on Fe-implanted ZnO (Fe-ZnO) thin film has been demonstrated. Implantation of Fe in rf-sputtered ZnO thin film introduces redox center along with shallow donor level and thereby enhance its electron transfer property. Glucose oxidase (GOx), chosen as model enzyme, has been immobilized on the surface of the matrix. Cyclic voltammetry and photometric assay show that the prepared bioelectrode, GOx/Fe-ZnO/ITO/Glass is sensitive to the glucose concentration with enhanced response of 0.326 μA mM−1 cm−2 and low Km of 2.76 mM. The results show promising application of Fe-implanted ZnO thin film as an attractive matrix for third generation biosensing.
Publisher: American Physical Society (APS)
Date: 15-12-2009
Publisher: Wiley
Date: 05-11-2007
Publisher: AIP Publishing
Date: 15-04-1996
DOI: 10.1063/1.115866
Abstract: Time resolved photoluminescence and electrical measurements were made on MeV As, Ga, Si, and O ion implanted GaAs to doses in the range of 1×1014–5×1016 cm−2 and subsequently annealed at 600 °C for 20 min under arsine ambient. Carrier trapping times were found to decrease with increase in implantation dose for all species studied and can be shorter than 1 ps. Sheet resistance values were found to be independent of implantation dose and were of the order of 108 Ω/⧠ for As, Ga, and O implantation and ∼2×102 Ω/⧠ for the Si case due to its electrical activation. Conductivity activation energies of 0.67–0.69 eV were observed for As, Ga, and O ion implanted and annealed GaAs, which are close to the reported activation energy for annealed low-temperature GaAs (0.65 eV).
Publisher: Elsevier BV
Date: 09-2014
Publisher: IEEE
Date: 06-2013
Publisher: Springer Science and Business Media LLC
Date: 25-07-2012
DOI: 10.1038/SREP00533
Publisher: AIP Publishing
Date: 15-07-2008
DOI: 10.1063/1.2959681
Abstract: This paper demonstrates an analytical expression for the quasistatic capacitance of a quantum dot layer embedded in a junction, where the reverse bias is used to discharge the initially occupied energy levels. This analysis can be used to determine the position and the Gaussian homogeneous broadening of the energy levels in the conduction band, and is applied for an InGaAs/GaAs quantum dot structure grown by metal organic chemical vapor deposition. It is shown that the Gaussian broadening of the conduction band levels is significantly larger than the broadening of the interband photoluminescence (PL) transitions involving both conduction and hole states. The analysis also reveals a contribution from the wetting layer both in PL and modeled C-V profiles which is much stronger than in typical molecular beam epitaxy grown dots. The presence of a built-in local field oriented from the apex of the dot toward its base, contrary to the direction expected for a strained dot with uniform composition (negative dipole), is also derived from fitting of the C-V experimental data.
Publisher: Springer Science and Business Media LLC
Date: 17-06-2016
DOI: 10.1038/NCOMMS11927
Abstract: Nanolasers hold promise for applications including integrated photonics, on-chip optical interconnects and optical sensing. Key to the realization of current cavity designs is the use of nanomaterials combining high gain with high radiative efficiency. Until now, efforts to enhance the performance of semiconductor nanomaterials have focused on reducing the rate of non-radiative recombination through improvements to material quality and complex passivation schemes. Here we employ controlled impurity doping to increase the rate of radiative recombination. This unique approach enables us to improve the radiative efficiency of unpassivated GaAs nanowires by a factor of several hundred times while also increasing differential gain and reducing the transparency carrier density. In this way, we demonstrate lasing from a nanomaterial that combines high radiative efficiency with a picosecond carrier lifetime ready for high speed applications.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2009
Publisher: AIP Publishing
Date: 11-07-2016
DOI: 10.1063/1.4958693
Abstract: Ion implantation of Zn substituting elements in ZnO has been shown to result in a dramatic Li depletion of several microns in hydrothermally grown ZnO. This has been ascribed to a burst of mobile Zn interstials. In this study, we seek to understand the reason behind this interstitial mediated transient enhanced diffusion in Li-containing ZnO s les after Zn implantation. ZnO wafers were implanted with Zn to two doses, 5 × 1015 cm−2 and 1 × 1017 cm−2. Secondary ion mass spectrometry was carried out to profile the Li depletion depth for different annealing temperatures between 600 and 800 °C. The 800 °C annealing had the most significant Li depletion of close to 60 μm. Transmission electron microscopy (TEM) was carried out in selected s les to identify the reason behind the Li depletion. In particular, TEM investigations of s les annealed at 750 °C show significant Zn precipitation just below the depth of the projected range of the implanted ions. We propose that the Zn precipitation is indicative of Zn supersaturation. Both the Li depletion and Zn precipitation are competing synchronous processes aimed at reducing the excess Zn interstitials.
Publisher: Elsevier BV
Date: 06-2000
Publisher: IOP Publishing
Date: 09-2023
Publisher: Institution of Engineering and Technology (IET)
Date: 1999
DOI: 10.1049/EL:19990078
Publisher: AIP Publishing
Date: 15-06-2012
DOI: 10.1063/1.4729833
Abstract: We report on a theoretical study of the relationship between interdiffusion and the conduction band optical absorption of In(Ga)As/GaAs quantum dots. Quantum dot geometries are progressively interdiffused based on Fick’s model and the quantum dot strain, band structure and optical absorption cross-section are calculated numerically. Quantifying the effects of interdiffusion on quantum dot optical absorption is important for applications that utilize post-growth techniques such as selective area intermixing.
Publisher: AIP Publishing
Date: 29-12-2003
DOI: 10.1063/1.1633349
Abstract: Semi-insulating InP was implanted with MeV P, As, Ga, and In ions, and the resulting evolution of structural properties with increased annealing temperature was analyzed using double crystal x-ray diffractometry and cross sectional transmission electron microscopy. The types of damage identified are correlated with scanning spreading resistance and scanning capacitance measurements, as well as with previously measured Hall effect and time resolved photoluminescence results. We have identified multiple layers of conductivity in the s les which occur due to the nonuniform damage profile of a single implant. Our structural studies have shown that the amount and type of damage caused by implantation does not scale with implant ion atomic mass.
Publisher: AIP Publishing
Date: 11-09-2006
DOI: 10.1063/1.2354432
Abstract: Stacked self-assembled In0.5Ga0.5As∕GaAs quantum dot infrared photodetectors grown by low-pressure metal-organic chemical vapor deposition, with and without silicon dopants in the quantum dot layers, are investigated. The increase of dark currents observed at higher doping levels is attributed to higher defect density leading to stronger sequential resonant tunneling and to lowering of the operating temperature of the device.
Publisher: IEEE
Date: 12-2014
Publisher: Elsevier BV
Date: 06-2001
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2004
Publisher: American Chemical Society (ACS)
Date: 04-02-2010
DOI: 10.1021/NL903547R
Abstract: Highly strained GaAs/GaP nanowires of excellent optical quality were grown with 50 nm diameter GaAs cores and 25 nm GaP shells. Photoluminescence from these nanowires is observed at energies dramatically shifted from the unstrained GaAs free exciton emission energy by 260 meV. Using Raman scattering, we show that it is possible to separately measure the degree of compressive and shear strain of the GaAs core and show that the Raman response of the GaP shell is consistent with tensile strain. The Raman and photoluminescence measurement are both on good agreement with 8 band k.p calculations. This result opens up new possibilities for engineering the electronic properties of the nanowires for optimal design of one-dimensional nanodevices by controlling the strain of the core and shell by varying the nanowire geometry.
Publisher: Elsevier BV
Date: 05-2009
Publisher: SPIE
Date: 28-08-2008
DOI: 10.1117/12.793568
Publisher: American Chemical Society (ACS)
Date: 16-11-2015
DOI: 10.1021/ACS.NANOLETT.5B04039
Abstract: In this Letter, we explore the nature of exciton localization in single GaAs/AlGaAs nanowire quantum well tube (QWT) devices using photocurrent (PC) spectroscopy combined with simultaneous photoluminescence (PL) and photoluminescence excitation (PLE) measurements. Excitons confined to GaAs quantum well tubes of 8 and 4 nm widths embedded into an AlGaAs barrier are seen to ionize at high bias levels. Spectroscopic signatures of the ground and excited states confined to the QWT seen in PL, PLE, and PC data are consistent with simple numerical calculations. The demonstration of good electrical contact with the QWTs enables the study of Stark effect shifts in the sharp emission lines of excitons localized to quantum dot-like states within the QWT. Atomic resolution cross-sectional TEM measurements and an analysis of the quantum confined Stark effect of these dots provide insights into the nature of the exciton localization in these nanostructures.
Publisher: IOP Publishing
Date: 15-12-2010
Publisher: IEEE
Date: 2000
Publisher: AIP Publishing
Date: 28-08-2013
DOI: 10.1063/1.4819216
Abstract: We studied the structural properties, defect formation, and thermal stability of H in hydrothermally grown ZnO single crystals implanted with H- dose ranging from 2.5×1016 to 1×1017 cm−2. H implantation is found to create deformed layers with a uniaxial strain of 0.5–2.4% along the c-axis in ZnO, for the low and high dose, respectively. About 0.2–0.4% of the original implanted H concentration can still be detected in the s les by secondary ion mass spectrometry after annealing at a temperature up to 800 °C. The thermally stable H is tentatively attributed to H related defect complexes involving the substitutional H that are bound to O vacancies and/or the highly mobile interstitial H that are bound to substitutional Li occupying Zn vacancies as the s les are cooled slowly from high temperature annealing. H implantation to a dose of 1×1017 cm−2 and followed by annealing at 800 °C, is found to result in the formation of vacancy clusters that evolved into faceted voids with diameter varying from 2 to 30 nm. The truncations around the voids form more favorably on the O-terminated surface than on the Zn-terminated surface, suggesting that O is a preferred surface polarity for the internal facets of the voids in the presence of H.
Publisher: Elsevier BV
Date: 05-2012
Publisher: American Chemical Society (ACS)
Date: 21-10-2013
DOI: 10.1021/NL402244P
Abstract: Manipulating the composition and morphology of semiconductor nanowires in a precisely controlled fashion is critical in developing nanowire devices. This is particularly true for ternary III-V nanowires. Many studies have shown the complexities within those nanowires. Here we report our findings of compositional irregularity in the shells of core-shell InGaAs nanowires with zinc-blende structure. Such an effect is caused by the crystal polarity within III-V zinc-blende lattice and the one-dimensional nature of nanowires that allows the formation of opposite polar surfaces simultaneously on the nanowire sidewalls. This polarity-driven effect in III-V nanowires may be utilized in manipulating the composition and morphology of III-V nanowires for device applications.
Publisher: Wiley
Date: 18-12-2022
Abstract: The realization of on‐chip microlasers with out‐of‐plane, controllable emission direction has been one of the core research themes in modern photonics. Traditional approaches for directional light scattering, including plasmonic nanoantennas and passive dielectric metasurfaces, are not suitable for on‐chip integration due to potential metallic contamination and reliance on external light sources. Meanwhile, achieving directional emission in active III–V microcavity lasers remains challenging due to geometrical symmetry and large free‐space coupling losses. Here, a novel approach is presented to realize directional lasing in an all‐dielectric, bottom‐up grown material system by coupling the laser emission from an InP microring cavity into a vertical nanowire at the ring center, which function as the photon source and directional antenna in the system, respectively. Efficient optical coupling is facilitated by enhanced light scattering at specific sidewall facets of the microring cavity, which can be engineered deterministically during epitaxial growth. Through Fourier imaging, out‐of‐plane laser emission with antenna‐like far‐field directivity in the coupled system is demonstrated. Furthermore, the emission directivity and side mode suppression in the coupled system can be improved significantly by tuning the geometric parameters of the system. The way for low power consumption, on‐chip microlasers with tunable emission directionality is paved here.
Publisher: IOP Publishing
Date: 07-08-2001
Publisher: Elsevier BV
Date: 02-2001
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8NR00737C
Abstract: After nitridation, nanorods show better optical properties, while their polarity changes from mixed-to N-polarity.
Publisher: AIP Publishing
Date: 15-02-2001
DOI: 10.1063/1.1339857
Abstract: Photoconductors based on V-grooved Al0.5Ga0.5As/GaAs multiple quantum wires (QWR) were fabricated. The geometric structure of the QWR was carefully characterized by transmission electron microscopy and spatially resolved microphotoluminescence measurements. Infrared response at 9.2 μm is observed from the photocurrent spectrum measured at 80 K. It is attributed as the intersubband transition in the quantum wire region. Due to the effective quantum confinement from the two (111)-surfaces forming the V groove, the overlapping between the ground state in the QWR and the one in the vertical quantum well is very small. This explains the weak photocurrent signal from the QWR photodetector. Theoretical design for a better wave function overlapping and optical coupling is outlined from the analysis of two-dimensional spatial distributions of the wave functions.
Publisher: IEEE
Date: 12-2014
Publisher: IEEE
Date: 2005
Publisher: IOP Publishing
Date: 20-07-2007
Publisher: OSA
Date: 2017
Publisher: AIP Publishing
Date: 25-03-2003
DOI: 10.1063/1.1561153
Abstract: Proton irradiation was used to create interdiffusion in In0.5Ga0.5As quantum dots (QDs), grown by low-pressure metalorganic chemical vapor deposition. After 25-keV proton irradiation, the QD s les were annealed at two temperatures (700 or 750 °C) for 30 s. It was found that much lower annealing temperatures were needed to recover the photoluminescence signals than in the quantum-well case. Large blueshifts (120 meV) and narrowing of the photoluminescence spectra were seen. Various doses (5×1013–1×1015 cm−2) and implant temperatures (20–200 °C) were used to study the interdiffusion processes in these s les. In QD s les, much lower doses were required to achieve similar energy shifts than reported in quantum-well s les.
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C0NR00128G
Abstract: We report on a detailed analysis of the effects of doping on the main device parameters of In(0.5)Ga(0.5)As/GaAs/Al(0.2)Ga(0.8)As quantum dots-in-a-well infrared photodetectors. Due to the relatively large conduction band offset of GaAs/Al(0.2)Ga(0.8)As (167 meV) transitions from wetting layer to quantum well states are observed for the highly doped devices. Since increasing the doping concentration fills the quantum dot states, electrons are forced to occupy the one-dimensional wetting layer states and therefore have quantum-well-like properties. This has facilitated a comparative study of the effects of three-dimensional and one-dimensional confinement of electrons on device parameters such as the responsivity and dark current by studying one particular detector structure with different doping concentrations of the active region.
Publisher: AIP Publishing
Date: 16-06-2005
DOI: 10.1063/1.1951051
Abstract: We have developed a terahertz radiation detector that measures both the litude and polarization of the electric field as a function of time. The device is a three-contact photoconductive receiver designed so that two orthogonal electric-field components of an arbitrary polarized electromagnetic wave may be detected simultaneously. The detector was fabricated on Fe+ ion-implanted InP. Polarization-sensitive detection is demonstrated with an extinction ratio better than 100:1. This type of device will have immediate application in studies of birefringent and optically active materials in the far-infrared region of the spectrum.
Publisher: American Chemical Society (ACS)
Date: 07-06-2012
DOI: 10.1021/NL300015W
Abstract: Surface states in semiconductor nanowires (NWs) are detrimental to the NW optical and electronic properties and to their light emission-based applications, due to the large surface-to-volume ratio of NWs and the congregation of defects states near surfaces. In this paper, we demonstrated an effective approach to eliminate surface states in InAs NWs of zinc-blende (ZB) and wurtzite (WZ) structures and a dramatic recovery of band edge emission through surface passivation with organic sulfide octadecylthiol (ODT). Microphotoluminescence (PL) measurements were carried out before and after passivation to study the dominant recombination mechanisms and surface state densities of the NWs. For WZ-NWs, we show that the passivation removed the surface states and recovered the band-edge emission, leading to a factor of ∼19 reduction of PL linewidth. For ZB-NWs, the deep surface states were removed and the PL peaks width became as narrow as ∼250 nm with some remaining emission of near band-edge surface states. The passivated NWs showed excellent stability in atmosphere, water, and heat environments. In particular, no observable changes occurred in the PL features from the passivated NWs exposed in air for more than five months.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2005
Publisher: The Optical Society
Date: 25-09-2012
DOI: 10.1364/OE.20.023281
Publisher: American Chemical Society (ACS)
Date: 25-02-2013
DOI: 10.1021/NL304182J
Abstract: The electronic properties of thin, nanometer scale GaAs quantum well tubes embedded inside the AlGaAs shell of a GaAs core-multishell nanowire are investigated using optical spectroscopies. Using numerical simulations to model cylindrically and hexagonally symmetric systems, we correlate these electronic properties with structural characterization by aberration-corrected scanning transmission electron microscopy of nanowire cross sections. These tubular quantum wells exhibit extremely high quantum efficiency and intense emission for extremely low submicrowatt excitation powers in both photoluminescence and photoluminescence excitation measurements. Numerical calculations of the confined eigenstates suggest that the electrons and holes in their ground states are confined to extremely localized one-dimensional filaments at the corners of the hexagonal structure which extend along the length of the nanowire.
Publisher: AIP Publishing
Date: 03-11-1997
DOI: 10.1063/1.120177
Abstract: Proton irradiation followed by rapid thermal annealing was used to selectively induce layer intermixing and thus shift the emission wavelengths of GaAs–AlGaAs graded-index separate-confinement-heterostructure quantum well lasers. Up to 40 nm shifts were observed in 4 μm ridge waveguide devices irradiated to a dose of 1.5×1016 cm−2. Although the wavelength shifts were accompanied by some degradation in the lasing threshold current and differential quantum efficiency, they were still quite acceptable at moderate wavelength shifts. This technique provides a simple and promising postgrowth process of integrating lasers of different wavelengths for wavelength- ision-multiplexing applications.
Publisher: Elsevier BV
Date: 10-2016
Publisher: AIP Publishing
Date: 09-2000
DOI: 10.1063/1.1287119
Abstract: Asymmetric double GaAs/AlGaAs V-grooved quantum wires, grown by low pressure metalorganic chemical vapor deposition, are studied using photoluminescence (PL) spectroscopy. The structure was selectively treated by ion implantation at different arsenic (As) doses after growth. The ion implantation strongly reduces the efficiency of the emissions from the implanted well regions or even quenches the PL emissions from certain well regions due to irradiation damage. Wire emission is clearly resolved in the s les after treatment by low dose implantation. The temperature dependence of the wire emission intensity shows an enhancement at a temperature of around 45 K. The wire emission peak with a shoulder at its high energy side at low temperatures develops into double peaks in a temperature region between 20 and 140 K, and the high energy transition component dominates the PL spectra at temperatures above 140 K. The deduced energy separation between two peaks is about 10 meV. With further increasing temperatures the wire emission related to the light hole state can be observed at temperatures above 150 K. Deduced splitting between the heavy and light states is about 35 meV in our structures.
Publisher: AIP Publishing
Date: 04-2004
DOI: 10.1063/1.1697628
Abstract: Microstructural and optical properties of InAs-inserted and reference single GaAsN/GaAs quantum-well (QW) structures grown by metalorganic chemical vapor deposition were investigated using cross-sectional transmission electron microscopy and photoluminescence (PL). Significant enhancement of PL intensity and a blueshift of PL emission were observed from the InAs-inserted GaAsN/GaAs QW structure, compared with the single GaAsN/GaAs QW structure. Strain compensation and In-induced reduction of N incorporation are suggested to be two major factors affecting the optical properties.
Publisher: IEEE
Date: 12-2012
Publisher: The Electrochemical Society
Date: 31-08-2013
Abstract: We present an overview of our work on improving the crystal quality and carrier lifetimes of our GaAs-based nanowires. These two properties are crucial for optoelectronic device applications and which we report by showing two ex les of nanowire lasers and nanowire solar cells.
Publisher: American Chemical Society (ACS)
Date: 08-03-2013
DOI: 10.1021/NL304170Q
Abstract: Devices based upon semiconductor nanowires provide many well-known advantages for next-generation photovoltaics, however, limited experimental techniques exist to determine essential electrical parameters within these devices. We present a novel application of a technique based upon two-photon induced photocurrent that provides a submicrometer resolution, three-dimensional reconstruction of photovoltaic parameters. This tool is used to characterize two GaAs nanowire-based devices, revealing the detail of current generation and collection, providing a path toward achieving the promise of nanowire-based photovoltaic devices.
Publisher: AIP Publishing
Date: 09-11-1998
DOI: 10.1063/1.122598
Abstract: Results of photoluminescence (PL) study of the self-organized InGaAs/GaAs quantum dots (QDs) in a field-effect structure grown by metalorganic vapor phase epitaxy are presented. It has been found that the PL from the QDs strongly depends on the bias voltage. No PL from the QDs ground state can be observed from the reverse biased structure, whereas the PL signal recovers in the forward biased structure. It is proposed that the bias dependence of the PL signal results from the QDs electron occupancy changes driven by the electric field within the structure. Due to a long thermalization time, the photogenerated electrons are swept out of the QDs by the electric field before radiative recombination. The electrically modulated PL (e-m PL), making use of the bias dependence of PL signal, is proposed as a tool for QD investigation. The e-m PL spectra at T=300 and T=4.2 K are analyzed and discussed.
Publisher: Elsevier BV
Date: 08-2005
Publisher: Elsevier BV
Date: 2005
Publisher: Elsevier BV
Date: 03-2011
Publisher: American Chemical Society (ACS)
Date: 21-05-2009
DOI: 10.1021/JP902843P
Publisher: AIP Publishing
Date: 13-01-2014
DOI: 10.1063/1.4861846
Abstract: We report the atomic-scale observation of parallel development of super elasticity and reversible dislocation-based plasticity from an early stage of bending deformation until fracture in GaAs nanowires. While this phenomenon is in sharp contrast to the textbook knowledge, it is expected to occur widely in nanostructures. This work indicates that the super recoverable deformation in nanomaterials is not simple elastic or reversible plastic deformation in nature, but the coupling of both.
Publisher: AIP Publishing
Date: 29-11-2010
DOI: 10.1063/1.3522889
Abstract: This paper presents a study on the strain relaxation and phonon confinement effect in InAsSb/InP quantum dashes (QDashes). The phonon mode with a frequency between that of InAs-like longitudinal optical mode and that of InP transverse optical mode is determined to be originated from InAsSb QDashes. Despite the small height of the QDashes, their phonon frequency is found to be mainly determined by the strain relaxation in the dashes. With increasing InAsSb deposition thickness and Sb composition in InAsSb dashes, the phonon mode shows an upward shift of its frequency due to the increased compressive strain.
Publisher: AIP Publishing
Date: 23-04-2007
DOI: 10.1063/1.2731729
Abstract: The authors demonstrate multiple wavelength lasers fabricated from InGaAs quantum dots. Selective area epitaxy is used to grow the active region, consisting of five layer stack of InGaAs quantum dots with different band gap energies in selected regions of the substrate, for fabrication of the lasers. The mechanism responsible for engineering of the band gap of quantum dots is discussed. The performance of the selectively grown lasers is compared to the lasers fabricated from structures grown in a standard, nonselective area growth process.
Publisher: IEEE
Date: 08-2007
Publisher: IOP Publishing
Date: 23-09-2016
DOI: 10.1088/0957-4484/27/43/435205
Abstract: Single nanowire (NW) green InGaN/GaN light-emitting diodes (LEDs) were fabricated by top-down etching technology. The electroluminescence (EL) peak wavelength remains approximately constant with an increasing injection current in contrast to a standard planar LED, which suggests that the quantum-confined Stark effect is significantly reduced in the single NW device. The strain relaxation mechanism is studied in the single NW LED using Raman scattering analysis. As compared to its planar counterpart, the EL peak of the NW LED shows a redshift, due to electric field redistribution as a result of changes in the cavity mode pattern after metallization. Our method has important implication for single NW optoelectronic device applications.
Publisher: IEEE
Date: 12-2012
Publisher: Proceedings of the National Academy of Sciences
Date: 20-11-2017
Abstract: Imaging chemical hysical reaction dynamics at nanoscale interfaces of a composite nanostructure requires resolutions in both space and time. Using single-pulse methodology, we directly and visually capture the irreversible eutectic-related phase reactions of a single, same metal/semiconductor nanowire at nanometer–nanosecond spatiotemporal resolution by 4D electron microscopy. With a nondestructive free-standing s le preparation free from environmental disturbance that is important for statistical investigation, we have both qualitatively and quantitatively elucidated the transient phase reactions and obtained important physical properties of the newly formed phases, such as latent heat and specific heat. Our work provides an efficient way of quantitatively determining physical properties of a nanoscale object with a tiny small quantity, especially when not available in bulk counterparts.
Publisher: AIP Publishing
Date: 15-05-2001
DOI: 10.1063/1.1365063
Abstract: The evolution of the sheet resistance (Rs) of n-type and p-type conductive InP layers during proton irradiation and the stability of the formed isolation during postirradiation annealing were investigated. It was found that the threshold dose (Dth) to convert the conductive layer to a highly resistive one is different for n- and p-type s les with similar initial free carrier concentrations. From our results, one infers that the antisite defects and/or related defect complexes formed by the replacement collisions are the carrier trapping centers, where InP is responsible for electron trapping and PIn for the hole trapping. A time dependence of the Rs was observed after each irradiation step to doses of ≅Dth and higher. This time variation is related to metastable processes involving free carriers. The thermal stability of the isolation of n-type s les is limited to temperatures lower than 200 °C, irrespectively of the irradiated dose. For p-type s les the thermal stability of electrical isolation is extended to 450–500 °C.
Publisher: Elsevier BV
Date: 04-2007
Publisher: AIP Publishing
Date: 18-02-2002
DOI: 10.1063/1.1449522
Abstract: The effect of two different dopants, P and Ga, in spin-on glass (SOG) films on impurity-free vacancy disordering (IFVD) in GaAs/AlGaAs quantum-well structures has been investigated. It is observed that by varying the annealing and baking temperatures, P-doped SOG films created a similar amount of intermixing as the undoped SOG films. This is different from the results of other studies of P-doped SiO2 and is ascribed to the low doping concentration of P, indicating that the doping concentration of P in the SiO2 layer is one of the key parameters that may control intermixing. On the other hand, for all the s les encapsulated with Ga-doped SOG layers, significant suppression of the intermixing was observed, making them very promising candidates with which to achieve the selective-area defect engineering that is required for any successful application of IFVD.
Publisher: AIP Publishing
Date: 23-06-1997
DOI: 10.1063/1.119192
Abstract: We have fabricated an antiresonant Fabry–Perot saturable absorber (A-FPSA), for potential use in laser passive mode locking, using metalorganic vapor phase epitaxy followed by ion implantation and thermal annealing. We show that the implantation/annealing cycle shortens the free-carrier dwell time without degrading the other optical properties of the A-FPSA.
Publisher: The Optical Society
Date: 28-03-2013
DOI: 10.1364/OE.21.008276
Publisher: IOP Publishing
Date: 16-03-2017
Abstract: In this work, we report on the photoelectrochemical (PEC) investigation of n-GaN nanopillar (NP) photoanodes fabricated using metal organic chemical vapour deposition and the top-down approach. Substantial improvement in photocurrents is observed for GaN NP photoanodes compared to their planar counterparts. The role of carrier concentration and NP dimensions on the PEC performance of NP photoanodes is further elucidated. Photocurrent density is almost doubled for doped NP photoanodes whereas no improvement is noticed for undoped NP photoanodes. While the diameter of GaN NP is found to influence the onset potential, carrier concentration is found to affect both the onset and overpotential of the electrodes. Optical and electrochemical impedance spectroscopy characterisations are utilised to further explain the PEC results of NP photoanodes. Finally, improvement in the photostability of NP photoanodes with the addition of NiO as a co-catalyst is investigated.
Publisher: IOP Publishing
Date: 27-03-2012
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2007
Publisher: IEEE
Date: 2002
Publisher: IEEE
Date: 10-2006
Publisher: AIP Publishing
Date: 22-10-2007
DOI: 10.1063/1.2802559
Abstract: We report on the spectral behavior of two different quantum dots-in-a-well infrared photodetectors grown by low-pressure metal-organic chemical vapor deposition. In0.5Ga0.5As quantum dots embedded in an In0.15Ga0.85As∕GaAs quantum well (QW) or a GaAs∕Al0.2Ga0.8As QW have been incorporated into photodetectors and were characterized. A spectral response in the 3–5μm atmospheric window has been achieved by adopting the GaAs∕Al0.2Ga0.8As QW.
Publisher: IEEE
Date: 09-2014
Publisher: IEEE
Date: 2003
Publisher: AIP Publishing
Date: 15-10-2003
DOI: 10.1063/1.1621089
Abstract: The electrical isolation of p-type GaAs1−xNx epilayers (x=0.6%, 1.4%, and 2.3%) produced by H, Li, C, or O ion implantation and its thermal stability in nominally undoped GaAs0.986N0.014 epilayers were investigated. Results show that the sheet resistance of p-type GaAsN layers can be increased by about five or six orders of magnitude by ion implantation and the threshold fluence (Fth) to convert a conductive layer to a highly resistive one depends on the original free carrier concentration and the number of implantation-generated atomic displacements, and does not depend on the nitrogen content. The thermal stability of electrical isolation in GaAsN depends on the ratio of the final fluence to the threshold fluence. The electrical isolation can be preserved up to 550 °C when the accumulated fluence is above 3.3 Fth.
Publisher: AIP Publishing
Date: 2007
DOI: 10.1063/1.2409612
Abstract: We report on the lasing characteristics of three- and five-stack InAs∕GaAs quantum dot (QD) lasers grown by metal organic chemical vapor deposition. By increasing the number of stacked dot layers to 5, lasing was achieved from the ground state at 1135nm for device lengths as short as 1.5mm (no reflectivity coatings). The un lified spontaneous emission and Z ratio as a function of injection current were also investigated. While the five-stack QD lasers behaved as expected with Z ratios of ≈2 prior to lasing, the three-stack QD lasers, which lased from the excited state, exhibited Z-ratio values as high as 4. A simple model was developed and indicated that high Z ratios can be generated by three nonradiative recombination pathways: (i) high monomolecular recombination within the wetting layer, (ii) Auger recombination involving carriers within the QDs (“unmixed” Auger), and (iii) Auger recombination involving both the QD and wetting layer states (“mixed” Auger), which dominate once the excited and wetting layer states become populated.
Publisher: Wiley
Date: 26-11-2013
Publisher: AIP Publishing
Date: 28-07-2011
DOI: 10.1063/1.3613679
Abstract: We demonstrate three-dimensional (3D) electronic spectroscopy of excitons in a double quantum well system using a three-dimensional phase retrieval algorithm to obtain the phase information that is lost in the measurement of intensities. By extending the analysis of two-dimensional spectroscopy to three dimensions, contributions from different quantum mechanical pathways can be further separated allowing greater insight into the mechanisms responsible for the observed peaks. By examining different slices of the complete three-dimensional spectrum, not only can the relative litudes be determined, but the peak shapes can also be analysed to reveal further details of the interactions with the environment and inhomogeneous broadening. We apply this technique to study the coupling between two coupled quantum wells, 5.7 nm and 8 nm wide, separated by a 4 nm barrier. Coupling between the heavy-hole excitons of each well results in a circular cross-peak indicating no correlation of the inhomogeneous broadening. An additional cross-peak is isolated in the 3D spectrum which is elongated in the diagonal direction indicating correlated inhomogeneous broadening. This is attributed to coupling of the excitons involving the two delocalised light-hole states and the electron state localised on the wide well. The attribution of this peak and the analysis of the peak shapes is supported by numerical simulations of the electron and hole wavefunctions and the three-dimensional spectrum based on a density matrix approach. An additional benefit of extending the phase retrieval algorithm from two to three dimensions is that it becomes substantially more reliable and less susceptible to noise as a result of the more extensive use of a priori information.
Publisher: AIP Publishing
Date: 02-2000
DOI: 10.1063/1.372051
Abstract: Intermixing induced by selective implantation was used to modify the two-dimensional (2D) quantum wells in the V-grooved quantum wire structure. Photoluminescence measurement of the implanted s les shows the obvious blueshift of the interband transition energy while quantum wire is not influenced by implantation. So the selective implantation method has been demonstrated in this article as a useful technique to isolate the energy levels of quantum wire structure from its neighbor 2D structures, which is preferred for the optoelectronic device application of quantum wire.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2013
Publisher: AIP Publishing
Date: 16-08-1999
DOI: 10.1063/1.124555
Abstract: Proton implantation and rapid thermal annealing were used to tune the infrared spectral response of quantum-well infrared photodetectors (QWIP) by up to 1.4 μm. Multiple proton implants at energies between 200 and 420 keV were used to create homogeneous quantum-well intermixing throughout the device’s multiple-quantum-well structure. Photoluminescence and spectral response measurements were used to study the effect of proton implantation on QWIPs for a series of doses up to 3.5×1015 protons cm−2. By using a mask during implantation, a method of constructing a color sensitive array is proposed.
Publisher: AIP Publishing
Date: 08-09-2008
DOI: 10.1063/1.2978959
Abstract: The structural and compositional characteristics of heterointerfaces of Au-catalyzed GaAs/InAs and InAs/GaAs axial nanowire heterostructures were comprehensively investigated by transmission electron microscopy. It has been found that the GaAs/InAs interface is not sharp and contains an InGaAs transition segment, and in contrast, the InAs/GaAs interface is atomically sharp. This difference in the nature of heterointerfaces can be attributed to the difference in the affinity of the group III elements with the catalyst material.
Publisher: The Electrochemical Society
Date: 2003
DOI: 10.1149/1.1588304
Publisher: AIP Publishing
Date: 15-10-2007
DOI: 10.1063/1.2800285
Abstract: This article analyzes compact laterally coupled distributed feedback (DFB) lasers with three defect regions. These devices are more flexible and smaller than conventional DFB lasers, having typical lengths between 20 and 50μm and a width less than 1μm (lateral gratings are inserted in a single-mode waveguide). We optimize the defect regions to achieve an improved performance. In other words, an adequate choice of phase shifts may lead to single-mode operation, lower threshold optical power, higher quantum differential efficiency, and more uniform field distribution. This device is designed to operate under optical pumping.
Publisher: IOP Publishing
Date: 27-09-2012
DOI: 10.1088/0957-4484/23/41/415702
Abstract: Vertically oriented GaAs nanowires (NWs) are grown on Si(111) substrates using metal-organic chemical vapor deposition. Controlled epitaxial growth along the direction is demonstrated following the deposition of thin GaAs buffer layers and the elimination of structural defects, such as twin defects and stacking faults, is found for high growth rates. By systematically manipulating the AsH(3) (group-V) and TMGa (group-III) precursor flow rates, it is found that the TMGa flow rate has the most significant effect on the nanowire quality. After capping the minimal tapering and twin-free GaAs NWs with an AlGaAs shell, long exciton lifetimes (over 700 ps) are obtained for high TMGa flow rate s les. It is observed that the Ga adatom concentration significantly affects the growth of GaAs NWs, with a high concentration and rapid growth leading to desirable characteristics for optoelectronic nanowire device applications including improved morphology, crystal structure and optical performance.
Publisher: Wiley
Date: 09-12-2011
Publisher: SPIE
Date: 09-02-2006
DOI: 10.1117/12.644074
Publisher: SPIE
Date: 27-12-2006
DOI: 10.1117/12.706526
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2015
Publisher: AIP Publishing
Date: 19-01-2005
DOI: 10.1063/1.1846140
Abstract: Impurity-free disordering (IFD) of uniformly doped p-GaAs epitaxial layers was achieved using either undoped or doped (Ga or P) spin-on-glass (SOG) in conjunction with rapid thermal annealing in the temperature range from 800to925°C. Capacitance-voltage measurements showed a pronounced increase in the doping concentration (NA) in the near-surface region of the layers disordered using both undoped and P:SOG. The increase in NA showed an Arrhenius-like dependence on the inverse of annealing temperature. On the other hand, NA did not change significantly for Ga-doped SOG. These changes can be explained by the relative injection of excess gallium vacancies (VGa) during IFD of p-GaAs by the different SOG layers. Deep-level transient spectroscopy showed a corresponding increase in the concentration of a defect HA (EV+0.39eV), which can be attributed to Cu, in the undoped and P:SOG disordered p-GaAs layers, but not in the epilayers disordered by Ga:SOG. We have explained the increase in free carrier concentration by the segregation of Zn atoms towards the surface during the injection of VGa. The redistribution of Zn during disordering of buried marker layers in GaAs and Al0.6Ga0.4As using either undoped or Ga-doped SOG was verified by secondary-ion mass spectrometry.
Publisher: AIP Publishing
Date: 10-05-2010
DOI: 10.1063/1.3428430
Abstract: Quantum wells with graded barriers are demonstrated as a means to control both the transition energy and electron-hole wave function overlap for quantum wells with an intrinsic internal electric field. In the case of c-axis grown ZnO/ZnMgO quantum wells, the graded barriers are produced by stepping the magnesium composition during the growth process. Four quantum wells with different structures are examined, where each well has similar transition energy, yet a wide range of wave function overlaps are observed. Photoluminescence and time resolved photoluminescence show good agreement with calculations.
Publisher: American Chemical Society (ACS)
Date: 22-09-2014
DOI: 10.1021/NL5027937
Abstract: With increasing interest in nanowire-based devices, a thorough understanding of the nanowire shape is required to gain tight control of the quality of nanowire heterostructures and improve the performance of related devices. We present a systematic study of the sidewalls of Au-catalyzed GaAs nanowires by investigating the faceting process from the beginning with vapor-liquid-solid (VLS) nucleation, followed by the simultaneous radial growth on the sidewalls, and to the end with sidewall transformation during annealing. The VLS nucleation interface of our GaAs nanowires is revealed by examining cross sections of the nanowire, where the nanowire exhibits a Reuleaux triangular shape with three curved surfaces along {112}A. These curved surfaces are not thermodynamically stable and adopt {112}A facets during radial growth. We observe clear differences in radial growth rate between the ⟨112⟩A and ⟨112⟩B directions with {112}B facets forming due to the slower radial growth rate along ⟨112⟩B directions. These sidewalls transform to {110} facets after high temperature (>500 °C) annealing. A nucleation model is proposed to explain the origin of the Reuleaux triangular shape of the nanowires, and the sidewall evolution is explained by surface kinetic and thermodynamic limitations.
Publisher: IOP Publishing
Date: 13-07-2010
DOI: 10.1088/0022-3727/43/30/302001
Abstract: This paper presents a study on the emission wavelength extension of InAsSb nanostructures using InGaAsSb sandwich layers. Due to the reduced lattice mismatch between InAsSb nanostructure layer and buffer/capping layer, the introduction of InGaAsSb sandwich layers leads to larger island size, reduced compressive strain and lower confinement barrier for InAsSb nanostructures, thus resulting in a longer emission wavelength. For InGaAsSb sandwich layers with nominal Sb concentration higher than 10%, type II band alignment is observed for the InAsSb/InGaAsSb heterostructure, which also contributes to the extension of emission wavelength. The InGaAsSb sandwich layers provide an effective approach to extend the emission wavelength of InAsSb nanostructures well beyond 2 µm, which is very useful for device applications in the mid-infrared region.
Publisher: SPIE-Intl Soc Optical Eng
Date: 10-2010
DOI: 10.1117/1.3490418
Publisher: AIP Publishing
Date: 05-2012
DOI: 10.1063/1.4710991
Abstract: The dopant dependence of photoluminescence (PL) from interstitial-related centers formed by ion implantation and a subsequent anneal in the range 175–525 °C is presented. The evolution of these centers is strongly effected by interstitial-dopant clustering even in the low temperature regime. There is a significant decrease in the W line (1018.2 meV) PL intensity with increasing B concentration. However, an enhancement is also observed in a narrow fabrication window in s les implanted with either P or Ga. The anneal temperature at which the W line intensity is optimized is sensitive to the dopant concentration and type. Furthermore, dopants which are implanted but not activated prior to low temperature thermal processing are found to have a more detrimental effect on the resulting PL. Splitting of the X line (1039.8 meV) arising from implantation damage induced strain is also observed.
Publisher: AIP Publishing
Date: 14-02-2022
DOI: 10.1063/5.0066507
Abstract: InAs nanowires have been considered as good candidates for infrared photodetection. However, one-dimensional geometry of a nanowire makes it unsuitable for broadband light absorption. In this work, we propose and design InAs nanosheet arrays to achieve polarization-independent, angle-insensitive, and ultrawide infrared absorption. Simulations demonstrate that two-dimensional InAs nanosheets can support multiple resonance modes, thus leading to a strong and broadband absorption from visible light to mid-wave infrared. Moreover, we can tune polarization-dependent property in InAs nanosheets to be polarization-insensitive by forming a nanosheet based clover-like and snowflake-like nanostructures. We further optimized the design of InAs nanosheet arrays based on such structures and achieved high absorption (up to 99.6%) covering a broad wavelength range from 500 to 3200 nm. These absorption properties are much superior to their nanowire and planar film counterparts, making it attractive for infrared photodetection applications. The architecture of such nanostructures can provide a promising route for the development of high-performance room-temperature broadband infrared photodetectors.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8NR08034H
Abstract: Cylindrical vector beams with radial and azimuthal polarizations are used to study harmonic generation from in idual AlGaAs nanoantennas.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2009
Publisher: Elsevier BV
Date: 11-2013
Publisher: American Chemical Society (ACS)
Date: 12-10-2022
Publisher: IOP Publishing
Date: 22-12-2018
Abstract: The research interest in photoelectrochemical (PEC) water splitting is ever growing due to its potential to contribute towards clean and portable energy. However, the lack of low energy band gap materials with high photocorrosion resistance is the primary setback inhibiting this technology from commercialisation. The ternary alloy InGaN shows promise to meet the photoelectrode material requirements due to its high chemical stability and band gap tunability. The band gap of InGaN can be modulated from the UV to IR regions by adjusting the In concentration so as to absorb the maximum portion of the solar spectrum. This paper reports on the influence of In concentration on the PEC properties of planar and nanopillar (NP) InGaN/GaN multi-quantum well (MQW) photoanodes, where NPs were fabricated using a top-down approach. Results show that changing the In concentration, while having a minor effect on the PEC performance of planar MQWs, has an enormous impact on the PEC performance of NP MQWs, with large variations in the photocurrent density observed. Planar photoanodes containing MQWs generate marginally lower photocurrents compared to photoanodes without MQWs when illuminated with sunlight. NP MQWs with 30% In generated the highest photocurrent density of 1.6 mA cm
Publisher: IEEE
Date: 12-2014
Publisher: Wiley
Date: 06-02-2009
Publisher: Springer Science and Business Media LLC
Date: 04-2003
Publisher: Elsevier BV
Date: 02-2001
Publisher: American Chemical Society (ACS)
Date: 04-05-2017
Publisher: IEEE
Date: 07-2008
Publisher: American Chemical Society (ACS)
Date: 05-01-2017
DOI: 10.1021/ACS.NANOLETT.6B04075
Abstract: A key task in the emerging field of bioelectronics is the transduction between ionic rotonic and electronic signals at high fidelity. This is a considerable challenge since the two carrier types exhibit intrinsically different physics and are best supported by very different materials types-electronic signals in inorganic semiconductors and ionic rotonic signals in organic or bio-organic polymers, gels, or electrolytes. Here we demonstrate a new class of organic-inorganic transducing interface featuring semiconducting nanowires electrostatically gated using a solid proton-transporting hygroscopic polymer. This model platform allows us to study the basic transducing mechanisms as well as deliver high fidelity signal conversion by tapping into and drawing together the best candidates from traditionally disparate realms of electronic materials research. By combining complementary n- and p-type transducers we demonstrate functional logic with significant potential for scaling toward high-density integrated bioelectronic circuitry.
Publisher: American Chemical Society (ACS)
Date: 02-07-2013
DOI: 10.1021/NL401680K
Abstract: AlGaAs/GaAs quantum well heterostructures based on core-multishell nanowires exhibit excellent optical properties which are acutely sensitive to structure and morphology. We characterize these heterostructures and observe them to have 3-fold symmetry about the nanowire axis. Using aberration-corrected annular dark field scanning transmission electron microscopy (ADF-STEM), we measure directly the polarity of the crystal structure and correlate this with the shape and facet orientation of the GaAs core, quantum wells and cap, and the width of radial Al-rich bands. We discuss how the underlying polarity of the crystal structure drives the growth of these heterostructures with a 3-fold symmetry resulting in a nonuniform GaAs quantum well tube and AlGaAs shell. These observations suggest that the AlGaAs growth rate is faster along the [112] B compared to the [112] A directions and/or that there is a polarity driven surface reconstruction generating AlGaAs growth fronts inclined to the {110} planes. In contrast, the observations suggest that the opposite is true for the GaAs growth, with the preferred surface reconstruction plane being parallel to {110} and an apparent faster growth rate along the [112] A. This two-dimensional layer growth of the nanowire multishells strongly depends on the surface energies and surface reconstruction of the facets which are related to the crystal polarity and lead to the 3-fold symmetry observed here.
Publisher: AIP Publishing
Date: 07-09-2009
DOI: 10.1063/1.3225148
Abstract: In this letter, we demonstrate that microphotoluminescence may be combined with optical trapping for effective optical characterization of single target InP semiconductor nanowires in suspension. Using this technique, we may investigate structural properties of optically trapped nanowires, such as crystalline polytypes and stacking faults. This arrangement may also be used to resolve structural variations along the axis of the trapped nanowire. These results show that photoluminescence measurements may be coupled with optical tweezers without degrading the performance of the optical trap and provide a powerful interrogation tool for preselection of components for nanowire photonic devices.
Publisher: IEEE
Date: 2002
Publisher: AIP Publishing
Date: 04-05-1998
DOI: 10.1063/1.121349
Abstract: In Si δ-modulation-doped GaAs/In0.2Ga0.8As/AlxGa1−xAs quantum well structures (QWs), the electrons from the ionized Si donors are initially confined in the V-shaped potential well (V-PW) formed at the position of a Si δ-doped layer. The efficiency of electrons transferring from the V-PW to the QW was investigated as a function of Si δ-doping concentration in the symmetric GaAs/In0.2Ga0.8As/GaAs QW at 1.7 K. The electron density in the QW increases linearly with an increase of Si δ-doping concentration, while the electron transfer efficiency remains unchanged either in the dark or under the illumination. The asymmetric GaAs/In0.2Ga0.8As/Al0.2Ga0.8As QW has a relatively higher electron transfer efficiency. The effect of grading the Al mole fraction over the AlxGa1−xAs spacer layer on the electron transfer efficiency was also reported.
Publisher: IEEE
Date: 12-2012
Publisher: AIP Publishing
Date: 07-11-2011
DOI: 10.1063/1.3659695
Abstract: Engineering the surface energy, interface energy, and elastic strain energy in the system via Sb exposure is used to realize the control on the morphology and optical properties of self-assembled InP-based InAsSb/InGaAs nanostructures. By flowing trimethylantimony precursor over the surface of InGaAs buffer layer before the growth of InAsSb nanostructures, the surface/interface energy in the system is reduced, while the strain energy in the system is enhanced, which lead to a shape transition from dot to dash, and to wire for the InAsSb nanostructures. As a result of their morphology changes, the InAsSb nanostructures show different polarization characteristics in their photoluminescence emission.
Publisher: IEEE
Date: 12-2014
Publisher: IEEE
Date: 2002
Publisher: AIP Publishing
Date: 15-10-2009
DOI: 10.1063/1.3248372
Abstract: GaAs thin films grown on Si (100) and (111) substrates by metal-organic chemical vapor deposition were investigated by electron microscopy. It was found that the growth rate of the GaAs epitaxial layers on Si (100) was faster than that on Si (111) due to a lower Si (111) surface energy. The morphologies and internal crystal structure quality of GaAs films grown on Si (111) were better than those grown on Si (100). It was also found that postannealing at high temperature can improve the morphology of the epitaxial layer surface and reduce lattice defects in the thin films.
Publisher: IEEE
Date: 12-2012
Publisher: IEEE
Date: 12-2012
Publisher: IEEE
Date: 12-2012
Publisher: IEEE
Date: 12-2012
Publisher: IEEE
Date: 2006
Publisher: IEEE
Date: 2004
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2006
Publisher: IEEE
Date: 12-2014
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 1998
DOI: 10.1109/2944.720473
Publisher: Lithuanian Academy of Sciences
Date: 28-03-2018
DOI: 10.3952/PHYSICS.V58I1.3648
Abstract: GaAs nanowires are promising candidates for advanced optoelectronic devices, despite their high surface recombination velocity and large surface-area-to-volume ratio, which renders them problematic for applications that require efficient charge collection and long charge-carrier lifetimes. Overcoating a bare GaAs nanowire core with an optimized larger-bandgap AlGaAs shell, followed by a capping layer of GaAs to prevent oxidation, has proven an effective way to passivate the nanowire surface and thereby improve electrical properties for enhanced device performance. However, it is difficult to quantify and distinguish the contributions between the nanowire core and cap layer when measuring the optoelectronic properties of a nanowire device. Here, we investigated the photoconductive terahertz (THz) response characteristics of single GaAs/AlGaAs/GaAs core–shell–cap nanowire detectors designed for THz time-domain spectroscopy. We present a detailed study of the contributions of the GaAs cap layer and GaAs core on the ultrafast optoelectronic performance of the detector. We show that both the GaAs cap and core contribute to the photoconductive signal in proportion to their relative volume in the nanowire. By increasing the cap volume ratio to above 90% of the total GaAs volume, a quasi-direct-s ling type photoconductive nanowire detector can be achieved that is highly desirable for low-noise and fast data acquisition detection.
Publisher: IEEE
Date: 12-2014
Publisher: Beilstein Institut
Date: 10-08-2018
DOI: 10.3762/BJNANO.9.201
Publisher: American Chemical Society (ACS)
Date: 15-02-2007
DOI: 10.1021/NL062383Q
Abstract: Nonequilibrium spin distributions in single GaAs/AlGaAs core-shell nanowires are excited using resonant polarized excitation at 10 K. At all excitation energies, we observe strong photoluminescence polarization due to suppressed radiative recombination of excitons with dipoles aligned perpendicular to the nanowire. Excitation resonances are observed at 1- or 2-LO phonon energies above the exciton ground states. Using rate equation modeling, we show that, at the lowest energies, strongly nonequilibrium spin distributions are present and we estimate their spin relaxation rate.
Publisher: IEEE
Date: 07-2014
DOI: 10.1109/SUM.2014.14
Publisher: IEEE
Date: 11-2010
Publisher: IEEE
Date: 2003
Publisher: American Chemical Society (ACS)
Date: 29-11-2012
DOI: 10.1021/NL3034027
Abstract: The ultrafast charge carrier dynamics in GaAs/conjugated polymer type II heterojunctions are investigated using time-resolved photoluminescence spectroscopy at 10 K. By probing the photoluminescence at the band edge of GaAs, we observe strong carrier lifetime enhancement for nanowires blended with semiconducting polymers. The enhancement is found to depend crucially on the ionization potential of the polymers with respect to the Fermi energy level at the surface of the GaAs nanowires. We attribute these effects to electron doping by the polymer which reduces the unsaturated surface-state density in GaAs. We find that when the surface of nanowires is terminated by native oxide, the electron injection across the interface is greatly reduced and such surface doping is absent. Our results suggest that surface engineering via π-conjugated polymers can substantially improve the carrier lifetime in nanowire hybrid heterojunctions with applications in photovoltaics and nanoscale photodetectors.
Publisher: IEEE
Date: 2003
Publisher: AIP Publishing
Date: 11-05-2005
DOI: 10.1063/1.1929874
Abstract: The mechanical properties of zinc oxide epitaxial layers grown on a- and c-axis sapphire have been studied by spherical nanoindentation and cross-sectional transmission electron microscopy. As-grown threading dislocations, which are characteristic of epitaxial material, combined with the presence of the much harder, underlying substrate are found to have a significant effect on the mechanical behavior of ZnO epilayers as compared to bulk material. Epilayer material is found to be significantly harder than its bulk counterpart. For a-axis epilayers, analysis of load–unload data yields a hardness of 6.6±1.2GPa, and 5.75±0.8GPa for c-axis layers. We attribute this increased hardness to strain compensation via the presence of as-grown defects. These defects inhibit the slip mechanism responsible for relative softness of bulk single crystals. The absence of pop-in events from analyzed continuous-load nanoindentation data is further evidence for strain compensation by native defects within the epilayers. Large variations in the spread of collected data are indicative of inhomegenity in the epilayers.
Publisher: American Chemical Society (ACS)
Date: 22-07-2015
DOI: 10.1021/ACS.NANOLETT.5B01603
Abstract: Determination of the elastic modulus of nanostructures with sizes at several nm range is a challenge. In this study, we designed an experiment to measure the elastic modulus of amorphous Al2O3 films with thicknesses varying between 2 and 25 nm. The amorphous Al2O3 was in the form of a shell, wrapped around GaAs nanowires, thereby forming an effective core/shell structure. The GaAs core comprised a single crystal structure with a diameter of 100 nm. Combined in situ compression transmission electron microscopy and finite element analysis were used to evaluate the elastic modulus of the overall core/shell nanowires. A core/shell model was applied to deconvolute the elastic modulus of the Al2O3 shell from the core. The results indicate that the elastic modulus of amorphous Al2O3 increases significantly when the thickness of the layer is smaller than 5 nm. This novel nanoscale material can be attributed to the reconstruction of the bonding at the surface of the material, coupled with the increase of the surface-to-volume ratio with nanoscale dimensions. Moreover, the experimental technique and analysis methods presented in this study may be extended to measure the elastic modulus of other materials with dimensions of just several nanometers.
Publisher: AIP Publishing
Date: 09-05-2003
DOI: 10.1063/1.1568533
Abstract: We have studied the photoluminescence properties of as-grown GaAs1−xNx epitaxial layers grown on GaAs containing 0.6%, 1.77%, and 2.8% nitrogen. We found laser emission from thick (d& nm) GaAs0.972N0.028 layers exhibiting the characteristic lasing properties of random lasers. This is unusual because random lasers have so far only been associated with highly disordered or random media. We believe that high gain in combination with structural inhomogeneities that are evident in these GaAs0.972N0.028 layers, can explain the random lasing in such epitaxial layers.
Publisher: OSA
Date: 2015
Publisher: IEEE
Date: 12-2012
Publisher: IEEE
Date: 12-2012
Publisher: Springer Science and Business Media LLC
Date: 22-03-2016
DOI: 10.1038/SREP23486
Abstract: Engineering metamaterials with tunable resonances are of great importance for improving the functionality and flexibility of terahertz (THz) systems. An ongoing challenge in THz science and technology is to create large-area active metamaterials as building blocks to enable efficient and precise control of THz signals. Here, an active metamaterial device based on enhancement-mode transparent amorphous oxide thin-film transistor arrays for THz modulation is demonstrated. Analytical modelling based on full-wave techniques and multipole theory exhibits excellent consistent with the experimental observations and reveals that the intrinsic resonance mode at 0.75 THz is dominated by an electric response. The resonant behavior can be effectively tuned by controlling the channel conductivity through an external bias. Such metal/oxide thin-film transistor based controllable metamaterials are energy saving, low cost, large area and ready for mass-production, which are expected to be widely used in future THz imaging, sensing, communications and other applications.
Publisher: IEEE
Date: 12-2012
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2003
Publisher: IEEE
Date: 12-2012
Publisher: IEEE
Date: 07-2007
Publisher: IEEE
Date: 2005
Publisher: IEEE
Date: 12-2012
Publisher: American Chemical Society (ACS)
Date: 09-11-2012
DOI: 10.1021/NL303787A
Abstract: We demonstrate luminescence from both the core and the shell of III-V semiconductor photonic nanowires by coupling them to plasmonic silver nanoparticles. This demonstration paves the way for increasing the quantum efficiency of large surface area nanowire light emitters. The relative emission intensity from the core and the shell is tuned by varying the polarization of the excitation source since their polarization response can be independently controlled. Independent control on emission wavelength and polarization dependence of emission from core-shell nanowire heterostructures opens up opportunities that have not yet been imagined for nanoscale polarization sensitive, wavelength-selective, or multicolor photonic devices based on single nanowires or nanowire arrays.
Publisher: AIP Publishing
Date: 12-1997
DOI: 10.1063/1.366439
Abstract: The dynamic properties of a sawtooth superlattice (δ-doped nipi) were examined by photoluminescence (PL) spectroscopic techniques. The structure was grown on a semi-insulating GaAs substrate by metalorganic vapor phase epitaxy, using C and Si δ-doping. The excitation intensity dependence of the s le’s PL was measured over six decades which produced a shift of 200 meV in the peak of the PL photon energy. The dynamic properties of the sawtooth superlattice were probed using time resolved PL and carrier lifetime measurements. Time resolved PL was measured over 6 orders of magnitude in delay time. The luminescence wavelength from the sawtooth superlattice s le was found to shift to low energies over time after pulsed excitation, indicating the temporal evolution of the band edges. A new and sensitive technique for measuring radiative recombination lifetimes at low excitation intensities was developed. Therefore δ-doped sawtooth superlattices are shown to have a tunable band gap as well as an intensity tunable carrier lifetime.
Publisher: Springer Science and Business Media LLC
Date: 17-11-2013
Publisher: IEEE
Date: 12-2012
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2NR02736D
Abstract: High-performance InAs nanowire transistors are realized by improving the surface and interfaces by coating with thermally oxidized Y 2 O 3.
Publisher: IEEE
Date: 12-2014
Publisher: IOP Publishing
Date: 28-02-2012
DOI: 10.1088/0957-4484/23/11/115603
Abstract: We investigate the growth procedures for achieving taper-free and kinked germanium nanowires epitaxially grown on silicon substrates by chemical vapor deposition. Singly and multiply kinked germanium nanowires consisting of segments were formed by employing a reactant gas purging process. Unlike non-epitaxial kinked nanowires, a two-temperature process is necessary to maintain the taper-free nature of segments in our kinked germanium nanowires on silicon. As an application, nanobridges formed between (111) side walls of V-grooved (100) silicon substrates have been demonstrated.
Publisher: American Chemical Society (ACS)
Date: 27-05-2011
DOI: 10.1021/CG2003657
Publisher: IEEE
Date: 06-2009
Publisher: IEEE
Date: 12-2014
Publisher: AIP Publishing
Date: 08-01-2001
DOI: 10.1063/1.1335552
Abstract: The deformation behavior of wurtzite GaN films modified by ion bombardment is studied by nanoindentation with a spherical indenter. Results show that implantation disorder significantly changes the mechanical properties of GaN. In particular, GaN amorphized by ion bombardment exhibits plastic deformation even for very low loads with dramatically reduced values of hardness and Young’s modulus compared to the values of as-grown GaN. Implantation-produced defects in crystalline GaN suppress the plastic component of deformation and significantly change the values of hardness and Young’s modulus. In addition, implantation disorder in crystalline GaN suppresses both “pop-in” events during loading and the appearance of slip traces on the s le surface as a result of indentation. This strongly suggests that slip nucleation (rather than a phase transformation) is the physical mechanism responsible for the pop-in events observed during loading of as-grown crystalline GaN.
Publisher: Cold Spring Harbor Laboratory
Date: 25-11-2022
DOI: 10.1101/2022.11.25.515889
Abstract: Human-induced pluripotent stem cell derived brain organoids provide models to study the human brain and its diseases. The neuronal activities of these organoids are recorded over time by Multi-electrode Arrays, calling for approaches to analyze their longitudinal variations to study the organoids’ electrophysiological maturation. We introduce a pipeline (Il-Vis) that incrementally learns and visualizes a progression trajectory representing the organoids’ electrophysiological properties. Unlike a static model that runs at the end of the experiment, Il-Vis generates a progression trajectory thus far at each s ling timepoint. Results on simulated data, for which the true progression trajectories are known, verified Il-Vis’s ability to capture and visualize the trajectories accurately and relative to each other. Results on brain organoid data revealed useful insights about organoids’ electrophysiological maturation stages and response patterns when exposed to Quinolinic Acid (and its blocking antibody), a metabolite contributing to many neuroinflammatory diseases including Alzheimer’s.
Publisher: Elsevier BV
Date: 12-2001
Publisher: Wiley
Date: 05-11-2018
DOI: 10.1002/PIP.3083
Publisher: Wiley
Date: 21-07-2010
Publisher: American Chemical Society (ACS)
Date: 22-07-2015
DOI: 10.1021/ACS.NANOLETT.5B01713
Abstract: We experimentally determine the lasing mode(s) in optically pumped semiconductor nanowire lasers. The spatially resolved and angle-resolved far-field emission profiles of single InP nanowire lasers lying horizontally on a SiO2 substrate are characterized in a microphotoluminescence (μ-PL) setup. The experimentally obtained polarization dependent far-field profiles match very well with numerical simulations and enable unambiguous identification of the lasing mode(s). This technique can be applied to characterize lasing modes in other type of nanolasers that are integrated on a substrate in either vertical or horizontal configurations.
Publisher: AIP Publishing
Date: 02-04-2021
DOI: 10.1063/5.0044706
Abstract: Selective area epitaxy (SAE) can be used to grow highly uniform III–V nanostructure arrays in a fully controllable way and is thus of great interest in both basic science and device applications. Here, an overview of this promising technique is presented, focusing on the growth fundamentals, formation of III–V nanowire arrays, monolithic integration of III–V nanowire arrays on silicon, the growth of nanowire heterostructures, and networks of various shapes. The applications of these III–V nanostructure arrays in photonics, electronics, optoelectronics, and quantum science are also reviewed. Finally, the current challenges and opportunities provided by SAE are discussed.
Publisher: Wiley
Date: 12-06-2013
Abstract: The optimal geometries for reducing the radiative recombination lifetime and thus enhancing the quantum efficiency of III-V semiconductor nanowires by coupling them to plasmonic nanoparticles are established. The quantum efficiency enhancement factor due to coupling to plasmonic nanoparticles reduces as the initial quality of the nanowire increases. Significant quantum efficiency enhancement is observed for semiconductors only within about 15 nm from the nanoparticle. It is also identified that the modes responsible for resonant enhancement in the quantum efficiency of an emitter in the nanowire are geometric resonances of surface plasmon polariton modes supported at the nanowire/nanoparticle interface.
Publisher: American Chemical Society (ACS)
Date: 14-07-2023
Publisher: Oxford University Press (OUP)
Date: 08-1987
DOI: 10.2307/1368635
Publisher: Springer Science and Business Media LLC
Date: 06-05-2009
DOI: 10.1007/S11671-009-9326-6
Abstract: GaAs was radially deposited on InAs nanowires by metal–organic chemical vapor deposition and resultant nanowire heterostructures were characterized by detailed electron microscopy investigations. The GaAs shells have been grown in wurtzite structure, epitaxially on the wurtzite structured InAs nanowire cores. The fundamental reason of structural evolution in terms of material nucleation and interfacial structure is given.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2006
Publisher: AIP Publishing
Date: 25-11-2002
DOI: 10.1063/1.1526913
Abstract: Radiative recombination at low temperatures in GaAsN is often associated with localized excitons. In this short note, we report results from high-resolution time-resolved photoluminescence spectroscopy that indicate that excitons, localized or otherwise, cannot be involved in the recombination process of this alloy system. The risetime of the photoluminescence signal is more than two orders of magnitude shorter than that expected, and found from excitonic recombination in other III–V materials, such as GaAs. We suggest that the radiative recombination in GaAsN takes place between localized electrons and delocalized holes.
Publisher: Optica Publishing Group
Date: 21-08-2008
Publisher: AIP Publishing
Date: 20-04-1998
DOI: 10.1063/1.121248
Abstract: We have investigated the photoexcited carrier dynamics in In1−xGaxAs/GaAs quantum wells using the photoluminescence up-conversion technique. We found a unique capture process which was exceptional both in terms of the capture time and its temperature dependence. In the case of a specific quantum well with wide barriers, the photoluminescence rise time, a parameter which includes the overall capture time and the exciton formation time, was less than 600 fs instead of the expected few hundred picoseconds. We show in this work that this unusually rapid process is the result of the capture of the photoexcited carriers (or excitons) by impurities in the GaAs barriers, from where they resonantly tunnel into the quantum well.
Publisher: AIP Publishing
Date: 14-02-2000
DOI: 10.1063/1.125601
Abstract: The quality of spin-on silica films prebaked at different temperatures has been studied using Fourier transform infrared spectroscopy, spectroscopic ellipsometry, and P-etch [HF(40%):HNO3(70%):H2O=3:2:60] measurements. Low-temperature photoluminescence (PL) was performed on GaAs/AlGaAs quantum-well (QW) structures encapsulated by the same films. For all the prebaked films, not only the Si–O–Si peaks, but also OH-related peaks were detected in the IR spectra. After annealing at 950 °C for 60 s, almost all OH-related peaks disappeared. Spectroscopic ellipsometry modeling and P-etch measurements showed that the porosity of high-temperature (& °C) baked s les was similar, and was significantly higher than the low-temperature (210 °C) baked s le. The same trend was observed in the PL energy shifts from the GaAs/AlGaAs QWs, indicating a direct correlation between the film quality and quantum-well intermixing.
Publisher: American Scientific Publishers
Date: 03-2010
Abstract: InAs quantum dots (QDs) are grown on InP or lattice matched GaInAsP buffers using horizontal flow metal-organic chemical vapor deposition (MOCVD) at a pressure of 180 mbar. A range of techniques, such as photoluminescence (PL), atomic force microscopy, and plan-view transmission electron microscopy is used to characterize the QD and other semiconductor layers. The effects of different growth parameters, such as V/III ratio and growth time, and the effects of buffer layers, interlayers, and cap layers are investigated and the optimized growth conditions are discussed. In the case of the QDs grown on InP buffers, the As/P exchange reaction is found to be prominent. A very thin (0.6 nm) GaAs interlayer grown between the buffer and the QD layers consumes segregated indium and minimizes the As/P exchange reaction. As a result, the QD PL emission energy increases, the PL intensity improves, and the PL linewidth decreases. The experimental results show that by changing the thickness of a GaAs interlayer (0.3-0.6 nm), the emission wavelength/energy of the QDs grown on a lattice matched GaInAsP buffer can be tuned over a wide range covering 1550 nm. However, further increase in the thickness of the GaAs interlayer results in the agglomeration of the QDs and the deterioration of the QD optical properties. Detailed microscopy studies show that capped QDs have higher density and are smaller in size on average compared to uncapped QDs, which undergo coalescence during cooling of the s le after growth. Overall, the QDs grown for shorter time with a smaller V/III ratio (approximately 8) show improved PL intensity and narrower PL linewidth.
Publisher: IOP Publishing
Date: 19-09-2018
Abstract: Impurity addition is a crucial aspect for III-V nanowire growth. In this study, we demonstrated the effect of the Sn addition on GaAs nanowire growth by metal-organic chemical vapor deposition. With increasing the tetraethyltin flow rate, the nanowire axial growth was suppressed while the nanowire lateral growth was promoted, as well as planar defects were increased. Systematic electron microscopy characterizations suggested that the Sn addition tuned the catalyst composition, changed the vapor-solid-liquid surfaces energies and hindered the Ga atoms diffusion on nanowire sidewalls, which is responsible for the observed changes in morphology and structural quality of grown GaAs nanowires. This study contributes to understanding the role of impurity dopants on III-V nanowires growth, which will be of benefit for the design and fabrication of future nanowire-based devices.
Publisher: Informa UK Limited
Date: 02-2005
Publisher: The Optical Society
Date: 04-2014
DOI: 10.1364/OE.22.008156
Publisher: Springer Science and Business Media LLC
Date: 12-2016
Publisher: American Chemical Society (ACS)
Date: 31-03-2015
Abstract: Semiconductor nanowires (NWs) formed by non-nitride III-V compounds grow preferentially with wurtzite (WZ) lattice. This is contrary to bulk and two-dimensional layers of the same compounds, where only zincblende (ZB) is observed. The absorption spectrum of WZ materials differs largely from their ZB counterparts and shows three transitions, referred to as A, B, and C in order of increasing energy, involving the minimum of the conduction band and different critical points of the valence band. In this work, we determine the temperature dependence (T = 10-310 K) of the energy of transitions A, B, and C in ensembles of WZ InP NWs by photoluminescence (PL) and PL excitation (PLE) spectroscopy. For the whole temperature and energy ranges investigated, the PL and PLE spectra are quantitatively reproduced by a theoretical model taking into account contribution from both exciton and continuum states. WZ InP is found to behave very similarly to wide band gap III-nitrides and II-VI compounds, where the energy of A, B, and C displays the same temperature dependence. This finding unveils a general feature of the thermal properties of WZ materials that holds regardless of the bond polarity and energy gap of the crystal. Furthermore, no differences are observed in the temperature dependence of the fundamental band gap energy in WZ InP NWs and ZB InP (both NWs and bulk). This result points to a negligible role played by the WZ/ZB differences in determining the deformation potentials and the extent of the electron-phonon interaction that is a direct consequence of the similar nearest neighbor arrangement in the two lattices.
Publisher: Springer Science and Business Media LLC
Date: 08-2003
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7NR04598K
Abstract: Wurtzite phase InP–In x Ga 1−x As nanowire radial quantum wells were grown for the first time, with tunable emission in the 1.3–1.55 μm optical communication wavelength range.
Publisher: AIP Publishing
Date: 12-06-1995
DOI: 10.1063/1.113738
Abstract: Nonstoichiometric GaAs obtained by implantation with 2 MeV arsenic ions at 1015 cm−2 dose is studied. As-implanted s les show a & fs lifetime of photocarriers and low resistivity due to hopping, with mobility less than 1 cm2/V s. Annealing of the s les at 600 °C leads to substantial recovery of postimplant damage, as seen from Rutherford backscattering channeling spectra and mobility increase to about 2000 cm2/V s, but photocarrier lifetime is still about 1 ps. These parameters are similar to those of low-temperature GaAs annealed at 600 °C, and make arsenic implanted GaAs an interesting material for optoelectronic applications.
Publisher: Springer Science and Business Media LLC
Date: 09-2012
DOI: 10.1557/MRC.2012.17
Publisher: Wiley
Date: 15-02-2011
Publisher: SPIE
Date: 09-02-2006
DOI: 10.1117/12.660717
Publisher: Elsevier BV
Date: 02-2001
Publisher: Elsevier BV
Date: 06-1993
Publisher: AIP Publishing
Date: 12-05-2008
DOI: 10.1063/1.2927487
Abstract: We report on the effects of the quantum well (QW) thickness on the spectral response and other characteristics of In0.5Ga0.5As∕GaAs∕Al0.2Ga0.8As quantum dots-in-a-well infrared photodetectors grown by low-pressure metal-organic chemical vapor deposition. The main device properties are observed to have a strong dependence on the QW parameters.
Publisher: American Scientific Publishers
Date: 12-2001
DOI: 10.1166/JNN.2001.064
Abstract: A pseudomorphic Al0.5Ga0.5As/In0.25Ga0.75As/GaAs asymmetric quantum wire (QWR) structure was grown on GaAs V-grooved substrate by low pressure metal organic vapor phase epitaxy. The formation of crescent shaped QWRs at the bottom of the V-grooves was confirmed by both transmission electron microscopy and photoluminescence (PL) spectra. The temperature dependence of PL spectra demonstrated a fast decrease of the sidewall quantum well PL intensity with increasing temperature, which originates from relaxation of carriers from well to wire region. The self-aligned dual implantation technique was successfully used to selectively disable the adjacent quantum structures. Decrease of the PL intensity of QWR at 8 K was observed after selective implantation, which resulted from a decreased number of carriers relaxed from adjacent quantum structures.
Publisher: IOP Publishing
Date: 29-11-2006
Publisher: Elsevier BV
Date: 04-2018
Publisher: Wiley
Date: 08-12-2008
Publisher: IEEE
Date: 2006
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2004
Publisher: AIP Publishing
Date: 15-03-2002
DOI: 10.1063/1.1452759
Abstract: Electrical isolation of n-type GaN epilayers bombarded with MeV light ions is studied by energy dispersive x-ray spectrometry (EDS). We show that the maximum bremsstrahlung x-ray energy (the Duane–Hunt limit) can be used to monitor the isolation process in GaN. This method allows the dose region above the threshold dose for isolation to be conveniently studied, whereas the application of conventional (low-voltage) electrical techniques in this dose range with large sheet resistances of the material (≳1011 Ω/sq) is often impossible due to comparable parasitic resistances of the experimental setup. A correlation of EDS and resistance measurements of GaN strongly suggests that the magnitude of s le charging scales with the number of ion-beam-produced deep electron traps which are empty at equilibrium. The results presented demonstrate the utility of EDS as a powerful and simple technique to study electrical isolation in wide band-gap semiconductors.
Publisher: American Chemical Society (ACS)
Date: 18-10-2013
DOI: 10.1021/NL4023385
Abstract: The effects of AlGaAs shell thickness and growth time on the minority carrier lifetime in the GaAs core of GaAs/AlGaAs core-shell nanowires grown by metal-organic chemical vapor deposition are investigated. The carrier lifetime increases with increasing AlGaAs shell thickness up to a certain value as a result of reducing tunneling probability of carriers through the AlGaAs shell, beyond which the carrier lifetime reduces due to the diffusion of Ga-Al and/or impurities across the GaAs/AlGaAs heterointerface. Interdiffusion at the heterointerface is observed directly using high-angle annular dark field scanning transmission electron microscopy. We achieve room temperature minority carrier lifetimes of 1.9 ns by optimizing the shell growth with the intention of reducing the effect of interdiffusion.
Publisher: IOP Publishing
Date: 30-04-2015
DOI: 10.1088/0957-4484/26/20/205604
Abstract: Obtaining compositional homogeneity without compromising morphological or structural quality is one of the biggest challenges in growing ternary alloy compound semiconductor nanowires. Here we report growth of Au-seeded InxGa1-xAs nanowires via metal-organic vapour phase epitaxy with uniform composition, morphology and pure wurtzite (WZ) crystal phase by carefully optimizing growth temperature and V/III ratio. We find that high growth temperatures allow the InxGa1-xAs composition to be more uniform by suppressing the formation of typically observed spontaneous In-rich shells. A low V/III ratio results in the growth of pure WZ phase InxGa1-xAs nanowires with uniform composition and morphology while a high V/III ratio allows pure zinc-blende (ZB) phase to form. Ga incorporation is found to be dependent on the crystal phase favouring higher Ga concentration in ZB phase compared to the WZ phase. Tapering is also found to be more prominent in defective nanowires hence it is critical to maintain the highest crystal structure purity in order to minimize tapering and inhomogeneity. The InP capped pure WZ In0.65Ga0.35As core-shell nanowire heterostructures show 1.54 μm photoluminescence, close to the technologically important optical fibre telecommunication wavelength, which is promising for application in photodetectors and nanoscale lasers.
Publisher: American Physical Society (APS)
Date: 25-07-2008
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2012
Publisher: AIP Publishing
Date: 06-07-2009
DOI: 10.1063/1.3160738
Abstract: This paper presents a study on the formation and shape control of InAsSb/InP nanostructures on InP (001) substrates. For the formation of InAsSb nanostructures, incorporation of Sb atoms into InAs islands results in significant morphology change in the islands due to the surfactant effect of Sb atoms and the large strain in the system. And, shape control of InAsSb/InP nanostructures is achieved by optimizing their growth parameters. Low growth temperature and high growth rate will induce the formation of InAsSb elongated quantum dots, while high growth temperature and low growth rate will promote the formation of InAsSb quantum wires or dashes.
Publisher: AIP Publishing
Date: 21-05-2012
DOI: 10.1063/1.4720514
Abstract: N-type ZnO s les have been implanted with MeV Zn+ ions at room temperature to doses between 1×108 and 2×1010cm-2, and the defect evolution has been studied by capacitance-voltage and deep level transient spectroscopy measurements. The results show a dose dependent compensation by acceptor-like defects along the implantation depth profile, and at least four ion-induced deep-level defects arise, where two levels with energy positions of 1.06 and 1.2 eV below the conduction band increase linearly with ion dose and are attributed to intrinsic defects. Moreover, a re-distribution of defects as a function of depth is observed already at temperatures below 400 K.
Publisher: IEEE
Date: 09-2004
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2011
Publisher: American Chemical Society (ACS)
Date: 14-12-2022
Publisher: American Chemical Society (ACS)
Date: 22-02-2016
DOI: 10.1021/ACS.NANOLETT.5B05095
Abstract: Stacking faults (SFs) are commonly observed crystalline defects in III-V semiconductor nanowires (NWs) that affect a variety of physical properties. Understanding the effect of SFs on NW mechanical properties is critical to NW applications in nanodevices. In this study, the Young's moduli of GaAs NWs with two distinct structures, defect-free single crystalline wurtzite (WZ) and highly defective wurtzite containing a high density of SFs (WZ-SF), are investigated using combined in situ compression transmission electron microscopy and finite element analysis. The Young's moduli of both WZ and WZ-SF GaAs NWs were found to increase with decreasing diameter due to the increasing volume fraction of the native oxide shell. The presence of a high density of SFs was further found to increase the Young's modulus by 13%. This stiffening effect of SFs is attributed to the change in the interatomic bonding configuration at the SFs.
Publisher: IEEE
Date: 2002
Publisher: IEEE
Date: 12-2010
Publisher: AIP Publishing
Date: 05-04-1999
DOI: 10.1063/1.123724
Abstract: We have measured the nonlinear optical absorption of arsenic and oxygen implanted epitaxial GaAs for a range of ion doses and annealing temperatures. The response time, τA, and a parameter, Mmax, which characterizes the performance of the structures as modulators, are both reduced by implantation, and correspondingly the nonbleachable losses are increased. We show that similar combinations of (τA, Mmax) can be achieved using either ion species and various combinations of dose and annealing temperatures. Furthermore, the data were all located on a well-defined curve in the (τA, Mmax) plane, provided amorphization, which occurs at high implant doses, was avoided. We deduce that there exists a limit to the modulation if a specific response time is required.
Publisher: AIP Publishing
Date: 13-09-2022
DOI: 10.1063/5.0102617
Abstract: Wafer-scale thin films of hexagonal boron nitride have exceptional thermal and mechanical properties, which harness the potential use of these materials in two-dimensional electronic, device applications. Along with unavoidable defects, grains, and wrinkles, which develop during the growth process, underlying substrates influence the physical and mechanical properties of these films. Understanding the interactions of these large-scale films with different substrates is, thus, important for the implementation of this 2D system in device fabrication. MOVPE-grown 2 and 30 nm hBN/sapphire films of size 2 in. diameter are delaminated chemically and transferred on quartz, SiO2/Si, and sapphire substrates. The structural characteristics of these films are investigated by employing Raman spectroscopy. Our results suggest that not only the roughness but also the height modulation at the surface of the substrates play a pivotal role in determining substrate-mediated mechanical strain inhomogeneity in these films. The statistical analysis of the spectral parameters provides us with the overall characteristics of the films. Furthermore, a Stark difference in the thermal evolution of strain in these films depending on substrate materials is observed. It has been demonstrated that not only the differential thermal expansion coefficient of the substrates and the films, but also slippage of the latter during the thermal treatment determines the net strain in the films. The role of the slippage is significantly higher in 2 nm films than in 30 nm films. We believe that the observations provide crucial information on the structural characteristics of the substrate-coupled wafer-scale hBN films for their future use in technology.
Publisher: Wiley
Date: 05-10-2017
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2004
Publisher: AIP Publishing
Date: 05-1999
DOI: 10.1063/1.370291
Abstract: Proton irradiation with subsequent rapid thermal annealing was used to investigate intermixing of InGaAs/GaAs and InGaAs/AlGaAs quantum wells. Large photoluminescence (PL) energy shifts were observed in both materials. Comparatively, InGaAs/AlGaAs s les showed larger PL energy shifts than InGaAs/GaAs s les because of the presence of Al in the barriers and also better recovery of PL intensities, which is mainly due to dynamic annealing effects in AlGaAs during irradiation. Based on this, InGaAs/AlGaAs quantum-well lasers were fabricated and up to 49.3-nm-emission wavelength shift was observed in the proton-irradiated laser with no significant degradation in device characteristics.
Publisher: IEEE
Date: 2000
Publisher: Wiley
Date: 25-07-2013
Publisher: IEEE
Date: 08-2011
Publisher: AIP Publishing
Date: 06-05-2004
DOI: 10.1063/1.1707230
Abstract: A major obstacle in the growth of stacked dot structures with a large number of layers is the high degree of strain in the dot layers. Strain buildup can affect the nucleation of the dots, which may cause defects that are detrimental to device performance. In this work, thin GaP layers are inserted below the quantum dot (QD) layer in single and stacked In0.5Ga0.5As/GaAs QD structures. These layers counterbalance the strain caused by the previous layers. Changes in dot nucleation are observed for dots grown directly on GaP layers. The QDs are found to be smaller in width and height. The luminescence from these dots is blueshifted due to interdiffusion between the dots and the GaP buffer layer. In a single layer of dots, no change in dot formation is seen when a thin GaAs barrier layer is deposited between the GaP layer and the QD layer. However, in stacked structures, the addition of a GaP layer below each QD layer is found to increase the density of the dots in the top layer of the stack. The room-temperature photoluminescence intensity is also increased.
Publisher: American Chemical Society (ACS)
Date: 02-12-2011
DOI: 10.1021/CG2008914
Publisher: IOP Publishing
Date: 29-06-2010
DOI: 10.1088/0957-4484/21/29/295602
Abstract: We demonstrate a method to realize vertically oriented Ge nanowires on Si(111) substrates. Ge nanowires were grown by chemical vapor deposition using Au nanoparticles to seed nanowire growth via a vapor-liquid-solid growth mechanism. Rapid oxidation of Si during Au nanoparticle application inhibits the growth of vertically oriented Ge nanowires directly on Si. The present method employs thin Ge buffer layers grown at low temperature less than 600 degrees C to circumvent the oxidation problem. By using a thin Ge buffer layer with root-mean-square roughness of approximately 2 nm, the yield of vertically oriented Ge nanowires is as high as 96.3%. This yield is comparable to that of homoepitaxial Ge nanowires. Furthermore, branched Ge nanowires could be successfully grown on these vertically oriented Ge nanowires by a secondary seeding technique. Since the buffer layers are grown under moderate conditions without any high temperature processing steps, this method has a wide process window highly suitable for Si-based microelectronics.
Publisher: American Chemical Society (ACS)
Date: 28-07-2011
DOI: 10.1021/NL202051W
Abstract: One of the main motivations for the great interest in semiconductor nanowires is the possibility of easily growing advanced heterostructures that might be difficult or even impossible to achieve in thin films. For III-V semiconductor nanowires, axial heterostructures with an interchange of the group III element typically grow straight in only one interface direction. In the case of InAs-GaAs heterostructures, straight nanowire growth has been demonstrated for growth of GaAs on top of InAs, but so far never in the other direction. In this article, we demonstrate the growth of straight axial heterostructures of InAs on top of GaAs. The heterostructure interface is sharp and we observe a dependence on growth parameters closely related to crystal structure as well as a diameter dependence on straight nanowire growth. The results are discussed by means of accurate first principles calculations of the interfacial energies. In addition, the role of the gold seed particle, the effect of its composition at different stages during growth, and its size are discussed in relation to the results observed.
Publisher: IEEE
Date: 1999
Publisher: SPIE
Date: 21-02-2018
DOI: 10.1117/12.2299831
Publisher: AIP Publishing
Date: 14-01-2008
DOI: 10.1063/1.2830998
Abstract: Self-sustained pulsations in the output power of metal-organic chemical vapor deposition grown ridge-waveguide lasers with InGaAs quantum dot active region are reported. The characteristics of the output power pulsations (range, frequency, and modulation depth) are presented. The origin of the pulsations is explained in terms of the properties of the quantum dot active region.
Publisher: American Physical Society (APS)
Date: 24-02-2016
Publisher: AIP Publishing
Date: 16-08-2002
DOI: 10.1063/1.1493651
Abstract: As + and P+ implantation was performed on semi-insulating (SI) and p-type InP s les for the purpose of creating a material suitable for ultrafast optoelectronic applications. SI InP s les were implanted with a dose of 1×1016 cm−2 and p-type InP was implanted with doses between 1×1012 and 1×1016 cm−2. Subsequently, rapid thermal annealing at temperatures between 400 and 700 °C was performed for 30 sec. Hall-effect measurements, double-crystal x-ray diffraction, and time-resolved femtosecond differential reflectivity showed that, for the highest-annealing temperatures, the implanted SI InP s les exhibited high mobility, low resistivity, short response times, and minimal structural damage. Similar measurements on implanted p-type InP showed that the fast response time, high mobility, and good structural recovery could be retained while increasing the resistivity.
Publisher: AIP Publishing
Date: 30-10-2006
DOI: 10.1063/1.2372747
Abstract: We have studied ZnO∕ZnMgO multiple quantum wells by spectrally resolved transient four-wave mixing with both one- and two-color excitations. The presence of an extended signal at negative interpulse delays in the two-color experiment is attributed to the two-photon coherence resulting from the generation of biexcitons. This technique provides a means to observe a transient four-wave mixing from biexcitons in the absence of any other signal, and thereby provides the first clear evidence that biexcitons are present in narrow ZnO∕ZnMgO quantum wells at room temperature. Dephasing times of the order of 100fs for the biexcitons are measured.
Publisher: AIP Publishing
Date: 04-12-2006
DOI: 10.1063/1.2398915
Abstract: The carrier dynamics of photoexcited electrons in the vicinity of the surface of (NH4)2S-passivated GaAs were studied via terahertz emission spectroscopy and optical-pump terahertz-probe spectroscopy. Terahertz emission spectroscopy measurements, coupled with Monte Carlo simulations of terahertz emission, revealed that the surface electric field of GaAs reverses after passivation. The conductivity of photoexcited electrons was determined via optical-pump terahertz-probe spectroscopy and was found to double after passivation. These experiments demonstrate that passivation significantly reduces the surface state density and surface recombination velocity of GaAs. Finally, it was demonstrated that passivation leads to an enhancement in the power radiated by photoconductive switch terahertz emitters, thereby showing the important influence of surface chemistry on the performance of ultrafast terahertz photonic devices.
Publisher: IEEE
Date: 12-2010
Publisher: AIP Publishing
Date: 05-10-2009
DOI: 10.1063/1.3246165
Abstract: This paper presents a study on the effect of matrix material on the morphology and optical properties of self-assembled InP-based InAsSb nanostructures. Due to the differences in surface roughness of the growth front, In0.53Ga0.47As matrix layer induces the formation of short quantum dashes (QDashes) and elongated quantum dots, while InP and In0.52Al0.48As matrix layers promote the formation of long QDashes and quantum wires, respectively. The shape anisotropy of InAsSb nanostructures on In0.53Ga0.47As, InP, and In0.52Al0.48As layers is further investigated with polarized photoluminescence measurements. The InAsSb nanostructures show a luminescence polarization degree of 8.5%, 14.3%, and 29% for In0.53Ga0.47As, InP, and In0.52Al0.48As matrixes, which corresponds well with the shape anisotropy observed with atomic force microscope. Furthermore, InAsSb/In0.53Ga0.47As nanostructures also show the longest, thermally stable emission wavelength, which serves as a promising material system for fabricating midinfrared emitters.
Publisher: IEEE
Date: 12-2010
Publisher: American Chemical Society (ACS)
Date: 25-07-2017
DOI: 10.1021/ACS.NANOLETT.7B01725
Abstract: Single nanowire lasers based on bottom-up III-V materials have been shown to exhibit room-temperature near-infrared lasing, making them highly promising for use as nanoscale, silicon-integrable, and coherent light sources. While lasing behavior is reproducible, small variations in growth conditions across a substrate arising from the use of bottom-up growth techniques can introduce interwire disorder, either through geometric or material inhomogeneity. Nanolasers critically depend on both high material quality and tight dimensional tolerances, and as such, lasing threshold is both sensitive to and a sensitive probe of such inhomogeneity. We present an all-optical characterization technique coupled to statistical analysis to correlate geometrical and material parameters with lasing threshold. For these multiple-quantum-well nanolasers, it is found that low threshold is closely linked to longer lasing wavelength caused by losses in the core, providing a route to optimized future low-threshold devices. A best-in-group room temperature lasing threshold of ∼43 μJ cm
Publisher: American Chemical Society (ACS)
Date: 03-03-2007
DOI: 10.1021/NL062755V
Abstract: We demonstrate vertically aligned epitaxial GaAs nanowires of excellent crystallographic quality and optimal shape, grown by Au nanoparticle-catalyzed metalorganic chemical vapor deposition. This is achieved by a two-temperature growth procedure, consisting of a brief initial high-temperature growth step followed by prolonged growth at a lower temperature. The initial high-temperature step is essential for obtaining straight, vertically aligned epitaxial nanowires on the (111)B GaAs substrate. The lower temperature employed for subsequent growth imparts superior nanowire morphology and crystallographic quality by minimizing radial growth and eliminating twinning defects. Photoluminescence measurements confirm the excellent optical quality of these two-temperature grown nanowires. Two mechanisms are proposed to explain the success of this two-temperature growth process, one involving Au nanoparticle-GaAs interface conditions and the other involving melting-solidification temperature hysteresis of the Au-Ga nanoparticle alloy.
Publisher: AIP Publishing
Date: 02-12-2004
DOI: 10.1063/1.1803948
Abstract: The effect of thermal interdiffusion on In(Ga)As∕GaAs quantum dot structures is very significant, due to the large strain and high concentration of indium within the dots. The traditional high temperature annealing conditions used in impurity free vacancy disordering of quantum wells cannot be used for quantum dots, as the dots can be destroyed at these temperatures. However, additional shifts due to capping layers can be achieved at low annealing temperatures. Spin-on-glass, plasma enhanced chemical vapor deposited SiO2, Si3N4, and electron-beam evaporated TiO2 layers are used to both enhance and suppress the interdiffusion in single and stacked quantum dot structures. After annealing at only 750°C the different cappings enable a shift in band gap energy of 100meV to be obtained across the s le.
Publisher: Elsevier BV
Date: 12-2000
Publisher: American Chemical Society (ACS)
Date: 10-07-2017
Abstract: The tightly bound biexcitons found in atomically thin semiconductors have very promising applications for optoelectronic and quantum devices. However, there is a discrepancy between theory and experiment regarding the fundamental structure of these biexcitons. Therefore, the exploration of a biexciton formation mechanism by further experiments is of great importance. Here, we successfully triggered the emission of biexcitons in atomically thin MoSe
Publisher: AIP Publishing
Date: 31-07-2000
DOI: 10.1063/1.127089
Publisher: The Optical Society
Date: 2007
DOI: 10.1364/OE.15.007047
Abstract: We report on the construction, optical alignment and performance of a receiver which is capable of recording the full polarization state of coherent terahertz radiation. The photoconductive detector was fabricated on InP which had been implanted with Fe(+) ions. The device operated successfully when it was gated with near infrared femtosecond pulses from either a Ti:sapphire laser oscillator or a 1 kHz regenerative laser lifier. When illuminated with terahertz radiation from a typical photoconductive source, the optimized device had a signal to noise figure of 100:1 with a usable spectral bandwidth of up to 4 THz. The device was shown to be very sensitive to terahertz polarization, being able to resolve changes in polarization of 0.34 degrees. Additionally, we have demonstrated the usefulness of this device for (i) polarization sensitive terahertz spectroscopy, by measuring the birefringence of quartz and (ii) terahertz emission experiments, by measuring the polarization dependence of radiation generated by optical rectification in (110)-ZnTe.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4TC02305F
Abstract: Spontaneous formation of core–shell GaAsP nanowires with P-enriched cores and As-enriched shells, demonstrating enhanced electrical conductivity.
Publisher: American Chemical Society (ACS)
Date: 28-07-2009
DOI: 10.1021/NL9016336
Abstract: We have used transient terahertz photoconductivity measurements to assess the efficacy of two-temperature growth and core-shell encapsulation techniques on the electronic properties of GaAs nanowires. We demonstrate that two-temperature growth of the GaAs core leads to an almost doubling in charge-carrier mobility and a tripling of carrier lifetime. In addition, overcoating the GaAs core with a larger-bandgap material is shown to reduce the density of surface traps by 82%, thereby enhancing the charge conductivity.
Publisher: American Physical Society (APS)
Date: 12-2004
Publisher: AIP Publishing
Date: 04-08-2008
DOI: 10.1063/1.2967877
Abstract: CW and time-resolved photoluminescence measurements are used to investigate exciton recombination dynamics in GaAs∕AlGaAs heterostructure nanowires grown with a recently developed technique which minimizes twinning. A thin capping layer is deposited to eliminate the possibility of oxidation of the AlGaAs shell as a source of oxygen defects in the GaAs core. We observe exciton lifetimes of ∼1ns, comparable to high quality two-dimensional double heterostructures. These GaAs nanowires allow one to observe state filling and many-body effects resulting from the increased carrier densities accessible with pulsed laser excitation.
Publisher: IEEE
Date: 11-2010
Publisher: AIP Publishing
Date: 1995
DOI: 10.1063/1.359358
Abstract: The nature of keV ion damage buildup and amorphization in AlxGa1−xAs at liquid-nitrogen temperature is investigated for various Al compositions using Rutherford backscattering channeling, transmission electron microscopy, and in situ time-resolved-reflectivity techniques. Two distinct damage buildup processes are observed in AlxGa1−xAs depending on Al content. At low Al content, the behavior is similar to GaAs whereby collisional disorder is ‘‘frozen in’’ and amorphization proceeds with increasing dose via the overlap of damage cascades and small amorphous zones created by in idual ion tracks. However, some dynamic annealing occurs during implantation in AlGaAs and this effect is accentuated with increasing Al content. For high Al content, crystallinity is retained at moderate ion damage with disorder building up in the form of stacking faults, planar, and other extended defects. In the latter case, amorphization is nucleation limited and proceeds abruptly when the level of crystalline disorder exceeds a critical level. The amorphization threshold dose increases with increasing Al composition by over two orders of magnitude from GaAs to AlAs. Dynamic annealing and damage creation processes during implantation compete very strongly in AlxGa1−xAs even at liquid-nitrogen temperatures. This behavior is discussed in terms of both the availability of very fast mobile defects and bonding configurational changes related to the Al sublattice in AlxGa1−xAs of high Al content.
Publisher: American Chemical Society (ACS)
Date: 30-03-2017
DOI: 10.1021/ACS.NANOLETT.7B00401
Abstract: Progress in the terahertz (THz) region of the electromagnetic spectrum is undergoing major advances, with advanced THz sources and detectors being developed at a rapid pace. Yet, ultrafast THz communication is still to be realized, owing to the lack of practical and effective THz modulators. Here, we present a novel ultrafast active THz polarization modulator based on GaAs semiconductor nanowires arranged in a wire-grid configuration. We utilize an optical pump-terahertz probe spectroscopy system and vary the polarization of the optical pump beam to demonstrate ultrafast THz modulation with a switching time of less than 5 ps and a modulation depth of -8 dB. We achieve an extinction of over 13% and a dynamic range of -9 dB, comparable to microsecond-switchable graphene- and metamaterial-based THz modulators, and surpassing the performance of optically switchable carbon nanotube THz polarizers. We show a broad bandwidth for THz modulation between 0.1 and 4 THz. Thus, this work presents the first THz modulator which combines not only a large modulation depth but also a broad bandwidth and picosecond time resolution for THz intensity and phase modulation, making it an ideal candidate for ultrafast THz communication.
Publisher: AIP Publishing
Date: 06-09-1999
DOI: 10.1063/1.124718
Abstract: Arsenic ion implantation with thermal annealing was used to shorten the response times of GaAs-based saturable absorber structures. Ultrafast absorption bleaching measurements indicated that the recovery time was decreased with increasing the implantation dose. However, above a certain dose the recovery time increased again. This behavior was correlated with the microstructure of the residual implantation defects.
Publisher: IEEE
Date: 2002
Publisher: American Chemical Society (ACS)
Date: 29-12-2015
DOI: 10.1021/NL503593W
Abstract: We demonstrate 900% relative enhancement in the quantum efficiency (QE) of surface passivated GaAs nanowires by coupling them to resonant nanocavities that support hybrid photonic-plasmonic modes. This nonconventional approach to increase the QE of GaAs nanowires results in QE enhancement over the entire nanowire volume and is not limited to the near-field of the plasmonic structure. Our cavity design enables spatially and spectrally tunable resonant modes and efficient in- and out-coupling of light from the nanowires. Furthermore, this approach is not fabrication intensive it is scalable and can be adapted to enhance the QE of a wide range of low QE semiconductor nanostructures.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2009
Publisher: IOP Publishing
Date: 17-12-2013
DOI: 10.1088/0022-3727/46/2/020301
Abstract: Energy and the environment are two of the most important global issues that we currently face. The development of clean and sustainable energy resources is essential to reduce greenhouse gas emission and meet our ever-increasing demand for energy. Over the last decade photovoltaics, as one of the leading technologies to meet these challenges, has seen a continuous increase in research, development and investment. Meanwhile, nanotechnology, which is considered to be the technology of the future, is gradually revolutionizing our everyday life through adaptation and incorporation into many traditional technologies, particularly energy-related technologies, such as photovoltaics. While the record for the highest efficiency is firmly held by multijunction III–V solar cells, there has never been a shortage of new research effort put into improving the efficiencies of all types of solar cells and making them more cost effective. In particular, there have been extensive and exciting developments in employing nanostructures features with different low dimensionalities, such as quantum wells, nanowires, nanotubes, nanoparticles and quantum dots, have been incorporated into existing photovoltaic technologies to enhance their performance and/or reduce their cost. Investigations into light trapping using plasmonic nanostructures to effectively increase light absorption in various solar cells are also being rigorously pursued. In addition, nanotechnology provides researchers with great opportunities to explore the new ideas and physics offered by nanostructures to implement advanced solar cell concepts such as hot carrier, multi-exciton and intermediate band solar cells. This special issue of Journal of Physics D: Applied Physics contains selected papers on nanostructured photovoltaics written by researchers in their respective fields of expertise. These papers capture the current excitement, as well as addressing some open questions in the field, covering topics including the III–V quantum well superlattice and quantum dot solar cells, Si quantum dot tandem cells, nanostructure-enhanced dye-sensitized solar cells and nanopatterned organic solar cells. We thank all the authors and reviewers for their contribution to this special issue. Special thanks are due to the journal's Publisher, Dr Olivia Roche and the editorial and publishing staff for their help and support.
Publisher: American Chemical Society (ACS)
Date: 03-12-2014
DOI: 10.1021/NL5036918
Abstract: The development of earth abundant materials for optoelectronics and photovoltaics promises improvements in sustainability and scalability. Recent studies have further demonstrated enhanced material efficiency through the superior light management of novel nanoscale geometries such as the nanowire. Here we show that an industry standard epitaxy technique can be used to fabricate high quality II-V nanowires (1D) and nanoplatelets (2D) of the earth abundant semiconductor Zn3As2. We go on to establish the optoelectronic potential of this material by demonstrating efficient photoemission and detection at 1.0 eV, an energy which is significant to the fields of both photovoltaics and optical telecommunications. Through dynamical spectroscopy this superior performance is found to arise from a low rate of surface recombination combined with a high rate of radiative recombination. These results introduce nanostructured Zn3As2 as a high quality optoelectronic material ready for device exploration.
Publisher: Elsevier BV
Date: 02-2009
Publisher: AIP Publishing
Date: 07-12-1998
DOI: 10.1063/1.122780
Abstract: We have used photoluminescence up conversion to study the carrier capture times into intermixed InGaAs/GaAs quantum wells. We have found that the capture into the intermixed wells is markedly faster than capture into the reference (unintermixed) quantum wells. The reasons for the significant reduction in the capture time is related to the shape of the intermixed quantum well. Such a reduction in the capture time is beneficial both in terms of the quantum efficiency and the frequency response of intermixed optoelectronic devices.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2003
Publisher: IOP Publishing
Date: 10-2008
Publisher: AIP Publishing
Date: 04-12-2006
DOI: 10.1063/1.2402234
Abstract: Highly lattice mismatched (7.8%) GaAs∕GaSb nanowire heterostructures were grown by metal-organic chemical vapor deposition and their detailed structural characteristics were determined by electron microscopy. The facts that (i) no defects have been found in GaSb and its interfaces with GaAs and (ii) the lattice mismatch between GaSb∕GaAs was fully relaxed suggest that the growth of GaSb nanowires is purely governed by the thermodynamics. The authors believe that the low growth rate of GaSb nanowires leads to the equilibrium growth.
Publisher: IEEE
Date: 12-2010
Publisher: Wiley
Date: 18-07-2017
Publisher: IOP Publishing
Date: 20-01-2006
Publisher: IEEE
Date: 07-2008
Publisher: Springer Science and Business Media LLC
Date: 25-09-2007
Publisher: AIP Publishing
Date: 08-1995
DOI: 10.1063/1.360237
Abstract: Deep levels and carrier compensation created in undoped metal-organic chemical-vapor deposition grown GaAs by low fluence proton irradiation (1×108−1×1010 cm−2) are investigated by the deep level transient spectroscopy technique and capacitance-voltage profiling. At least five main electron traps are observed after room-temperature irradiation in addition to the EL2 present in the as-grown material. Irradiation generates additional EL2, which annihilate at much lower temperatures than one would expect for isolated EL2. However, with further increase in irradiation fluence, the magnitude for this additional increment begin to decrease. The apparent decrease in the EL2 peak is accompanied by an increase of a broad peak in the deep level transient spectroscopic spectrum. This broad peak has a highly nonexponential capacitance transient and it is suggested to result from the interaction of the additional EL2 with EL6. One of the observed traps, with energy level, (Ec−0.40) eV, has not previously been reported in proton irradiated GaAs. The signature of this trap resembles that of EL5 and is quite stable at moderate annealing temperatures annihilating completely only at a temperature of ∼600 °C. This level shows a saturation effect with increasing irradiation dose and we believe it is related to complex defect-impurity formation. The temperature dependence of the carrier profiles reveals some complex behavior of carrier compensation, including acceptor- and donor-like properties of the various traps.
Publisher: IEEE
Date: 12-2010
Publisher: American Chemical Society (ACS)
Date: 12-06-2018
Abstract: The ability to manipulate light-matter interaction in semiconducting nanostructures is fascinating for implementing functionalities in advanced optoelectronic devices. Here, we report the tailoring of radiative emissions in a ZnTe/ZnTe:O/ZnO core-shell single nanowire coupled with a one-dimensional aluminum bowtie antenna array. The plasmonic antenna enables changes in the excitation and emission processes, leading to an obvious enhancement of near band edge emission (2.2 eV) and subgap excitonic emission (1.7 eV) bound to intermediate band states in a ZnTe/ZnTe:O/ZnO core-shell nanowire as well as surface-enhanced Raman scattering at room temperature. The increase of emission decay rate in the nanowire/antenna system, probed by time-resolved photoluminescence spectroscopy, yields an observable enhancement of quantum efficiency induced by local surface plasmon resonance. Electromagnetic simulations agree well with the experimental observations, revealing a combined effect of enhanced electric near-field intensity and the improvement of quantum efficiency in the ZnTe/ZnTe:O/ZnO nanowire/antenna system. The capability of tailoring light-matter interaction in low-efficient emitters may provide an alternative platform for designing advanced optoelectronic and sensing devices with precisely controlled response.
Publisher: IOP Publishing
Date: 15-10-2010
DOI: 10.1088/0022-3727/43/44/445402
Abstract: The effects of growth temperature and V/III ratio on the morphology and crystallographic phases of InP nanowires that are grown by metal organic chemical vapour deposition have been studied. We show that higher growth temperatures or higher V/III ratios promote the formation of wurtzite nanowires while zinc-blende nanowires are favourable at lower growth temperatures and lower V/III ratios. A schematic map of distribution of zinc-blende and wurtzite structures has been developed in the range of growth temperatures (400–510 °C) and V/III ratios (44 to 700) investigated in this study.
Publisher: Elsevier
Date: 2016
Publisher: IEEE
Date: 09-2018
Publisher: Elsevier BV
Date: 1997
Publisher: IEEE
Date: 12-2010
Publisher: IEEE
Date: 2002
Publisher: American Chemical Society (ACS)
Date: 23-10-2013
DOI: 10.1021/NL4028878
Abstract: We use polarized photoluminescence excitation spectroscopy to observe the energy and symmetry of the predicted second conduction band in 130 nm diameter wurtzite InP nanowires. We find direct spectroscopic signatures for optical transitions among the A, B, and C hole bands and both the first and the second conduction bands. We determine that the splitting between the first and second conduction bands is 228 ± 7 meV in excellent agreement with theory. From these energies we show that the spin-orbit energy changes substantially between zinc blende and wurtzite InP. We discuss the two quite different solutions within the quasi-cubic approximation and the implications for these measurements. Finally, the observation of well-defined optical transitions between the B- and C-hole bands and the second conduction band suggests that either the theoretical description of the second conduction band as possessing Γ8 symmetry is incomplete, or other interactions are enabling these forbidden transitions.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 1998
DOI: 10.1109/3.726608
Publisher: The Optical Society
Date: 20-06-2014
DOI: 10.1364/OE.22.015949
Publisher: IEEE
Date: 07-2017
Publisher: IOP Publishing
Date: 07-12-2009
DOI: 10.1088/0957-4484/21/3/035604
Abstract: Straight, vertically aligned GaAs nanowires were grown on Si(111) substrates coated with thin GaAs buffer layers. We find that the V/III precursor ratio and growth temperature are crucial factors influencing the morphology and quality of buffer layers. A double layer structure, consisting of a thin initial layer grown at low V/III ratio and low temperature followed by a layer grown at high V/III ratio and high temperature, is crucial for achieving straight, vertically aligned GaAs nanowires on Si(111) substrates. An in situ annealing step at high temperature after buffer layer growth improves the surface and structural properties of the buffer layer, which further improves the morphology of the GaAs nanowire growth. Through such optimizations we show that vertically aligned GaAs nanowires can be fabricated on Si(111) substrates and achieve the same structural and optical properties as GaAs nanowires grown directly on GaAs(111)B substrates.
Publisher: AIP Publishing
Date: 15-11-2001
DOI: 10.1063/1.1410317
Abstract: Transient band-gap renormalization (BGR) effects are investigated in AlGaAs/GaAs V-grooved quantum structures. The temperature-dependent transient BGR effects in the sidewall quantum well (SQWL) provide direct evidence of the existence of the blocking effect by the necking region barrier on the carrier trapping process. These effects provide a useful method to show the existence of the necking region, particularly for very thin SQWL structures. The temperature-dependent lifetimes of the SQWL and quantum wire (QWR) provide further proof of the carrier trapping process from the SQWL to the QWR.
Publisher: The Optical Society
Date: 09-01-2019
DOI: 10.1364/OE.27.000761
Publisher: American Chemical Society (ACS)
Date: 24-01-2019
DOI: 10.1021/ACS.NANOLETT.8B03870
Abstract: Nanoeutectic phase reaction covers the fundamental study of a chemical and physical reaction of multiple phases at the nanoscale. Here, we report the direct visualization of phase-reaction dynamics in Au/GaAs nanowires (NWs) using four-dimensional (4D) electron microscopy. The NW phase reactions were initiated with a pump laser pulse, while the following dynamics in the Au/GaAs NW was probed by a precisely time-delayed electron pulse. Single-pulse imaging reveals that the cubic zinc-blende NW presents a transient length increase within the time duration of ∼150 ns, giving the appearance of intermediate phase reactions at an early stage. A final length reduction of the NW is observed after the phase reactions have fully ended. In contrast, only length reduction is seen throughout the entire process in GaAs/AlGaAs core-shell and hexagonal wurtzite GaAs NWs. The reasons for the above intriguing phenomena are discussed. The eutectic-related phenomena in both zinc-blende and wurtzite materials offer a comprehensive understanding of phase-reaction dynamics in polytypic structures commonly available in compound semiconductors.
Publisher: Elsevier BV
Date: 2013
DOI: 10.1016/J.ULTRAMIC.2012.08.014
Abstract: Atom probe tomography (APT) is capable of simultaneously revealing the chemical identities and three dimensional positions of in idual atoms within a needle-shaped specimen, but suffers from a limited field-of-view (FOV), i.e., only the core of the specimen is effectively detected. Therefore, the capacity to analyze the full tip is crucial and much desired in cases that the shell of the specimen is also the region of interest. In this paper, we demonstrate that, in the analysis of III-V nanowires epitaxially grown from a substrate, the presence of the flat substrate positioned only micrometers away from the analyzed tip apex alters the field distribution and ion trajectories, which provides extra image compression that allows for the analysis of the entire specimen. An array of experimental results, including field desorption maps, elemental distributions, and crystallographic features clearly demonstrate the fact that the whole tip has been imaged, which is confirmed by electrostatic simulations.
Publisher: AIP Publishing
Date: 2001
DOI: 10.1063/1.1332984
Abstract: Single high-energy (0.9 MeV) proton implantation and rapid thermal annealing was used to tune the spectral response of the quantum-well infrared photodetectors (QWIPs). In addition to the large redshift of the QWIPs’ response wavelength after implantation, either narrowed or broadened spectrum was obtained at different interdiffusion extent. In general, the overall device performance for the low-dose implantation was not significantly degraded. In comparison with the other implantation schemes, this single high-energy implantation is the most effective and simple technique in tuning the wavelength of QWIPs, thus, to achieve the fabrication of multicolor detectors.
Publisher: IOP Publishing
Date: 10-03-2010
DOI: 10.1088/0957-4484/21/14/145602
Abstract: The two-dimensional heterostructure nanobelts with a central CdSe region and lateral CdS structures are synthesized by a two-step physical vapor transport method. The large growth rate difference between lateral CdS structures on both +/- (0001) sides of the CdSe region is found. The growth anisotropy is discussed in terms of the polar nature of the side +/- (0001) surfaces of CdSe. High-resolution transmission electron microscopy reveals the CdSe central region covered with non-uniform CdS layer/islands. From micro-photoluminescence measurements, a systematic blueshift of emission energy from the central CdSe region in accordance with the increase of lateral CdS growth temperature is observed. This result indicates that the intermixing rate in the CdSe region with CdS increases with the increase of lateral CdS growth temperature. In conventional CdSSe ternary nanostructures, morphology and emission wavelength were correlated parameters. However, the morphology and emission wavelength are independently controllable in the CdS/CdSe lateral heterostructure nanobelts. This structure is attractive for applications in visible optoelectronic devices.
Publisher: IEEE
Date: 2002
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2023
Publisher: AIP Publishing
Date: 25-02-2002
DOI: 10.1063/1.1455141
Publisher: Elsevier BV
Date: 10-2013
Publisher: Institution of Engineering and Technology (IET)
Date: 2005
Publisher: AIP Publishing
Date: 04-09-2000
DOI: 10.1063/1.1290722
Abstract: Wurtzite GaN films bombarded with heavy ions (197Au+) show anomalous swelling of the implanted region with corresponding volume expansion up to ∼50%. Results show that this phenomenon is due to the formation of a porous layer of amorphous GaN. An important implication of this study for the fabrication of GaN-based devices is that amorphization of GaN should be avoided during ion implantation.
Publisher: American Chemical Society (ACS)
Date: 02-05-2011
DOI: 10.1021/NL200720M
Abstract: We report on the optical trapping characteristics of InP nanowires with dimensions of 30 (±6) nm in diameter and 2-15 μm in length. We describe a method for calibrating the absolute position of in idual nanowires relative to the trapping center using synchronous high-speed position sensing and acousto-optic beam switching. Through brownian dynamics we investigate effects of the laser power and polarization on trap stability, as well as length dependence and the effect of simultaneous trapping multiple nanowires.
Publisher: Wiley
Date: 27-07-2015
Publisher: American Chemical Society (ACS)
Date: 05-06-2014
DOI: 10.1021/NN5017428
Abstract: Growth of III-V nanowires on the [100]-oriented industry standard substrates is critical for future integrated nanowire device development. Here we present an in-depth analysis of the seemingly complex ensembles of epitaxial nanowires grown on InP (100) substrates. The nanowires are categorized into three types as vertical, nonvertical, and planar, and the growth directions, facets, and crystal structure of each type are investigated. The nonvertical growth directions are mathematically modeled using a three-dimensional multiple-order twinning concept. The nonvertical nanowires can be further classified into two different types, with one type growing in the ⟨111⟩ directions and the other in the ⟨100⟩ directions after initial multiple three-dimensional twinning. We find that 99% of the total nanowires are grown either along ⟨100⟩, ⟨111⟩, or ⟨110⟩ growth directions by {100} or {111} growth facets. We also demonstrate relative control of yield of these different types of nanowires, by tuning pregrowth annealing conditions and growth parameters. Together, the knowledge and controllability of the types of nanowires provide an ideal foundation to explore novel geometries that combine different crystal structures, with potential for both fundamental science research and device applications.
Publisher: IOP Publishing
Date: 29-06-2018
Publisher: Elsevier BV
Date: 12-2003
Publisher: IOP Publishing
Date: 08-1994
Publisher: Elsevier
Date: 2017
Publisher: American Chemical Society (ACS)
Date: 03-01-2023
Publisher: IOP Publishing
Date: 20-02-2017
Abstract: Developing single-nanowire terahertz (THz) electronics and employing them as sub-wavelength components for highly-integrated THz time-domain spectroscopy (THz-TDS) applications is a promising approach to achieve future low-cost, highly integrable and high-resolution THz tools, which are desirable in many areas spanning from security, industry, environmental monitoring and medical diagnostics to fundamental science. In this work, we present the design and growth of n
Publisher: IOP Publishing
Date: 21-02-2008
DOI: 10.1088/0957-4484/19/12/125602
Abstract: The growth of epitaxial Ge nanowires is investigated on (100), (111) B and (110) GaAs substrates in the growth temperature range from 300 to 380 °C. Unlike epitaxial Ge nanowires on Ge or Si substrates, Ge nanowires on GaAs substrates grow predominantly along the [Formula: see text] direction. Using this unique property, vertical [Formula: see text] Ge nanowires epitaxially grown on GaAs(110) surface are realized. In addition, these Ge nanowires exhibit minimal tapering and uniform diameters, regardless of growth temperatures, which is an advantageous property for device applications. Ge nanowires growing along the [Formula: see text] directions are particularly attractive candidates for forming nanobridge devices on conventional (100) surfaces.
Publisher: AIP Publishing
Date: 04-1996
DOI: 10.1063/1.361377
Abstract: Using trimethylaluminum (TMAl) or trimethylgallium (TMGa) as a doping precursor, carbon δ-doped AlxGa1−xAs has been grown in metalorganic vapor phase epitaxy. Compared to TMGa, TMAl exhibits very high carbon δ-doping efficiency. The best hole profile of carbon δ-doped Al0.3Ga0.7As grown at 580 °C using TMAl as a doping precursor has a peak hole density of 1.6×1019 cm−3 for a full width at half-maximum of 85 Å with most of the incorporated carbon atoms being electrically active. When TMGa is used as the doping precursor, the hole density of carbon δ-doped AlxGa1−xAs significantly increases with an increase of the Al mole fraction. By comparison, the use of TMAl almost induces independence of the hole density on the Al mole fraction. The hole density of carbon δ-doped Al0.3Ga0.7As weakly increases when reducing the δ-doping temperature regardless of the doping precursors. The hole density of carbon δ-doped Al0.3Ga0.7As grown at 580 °C is proportionally associated with the moles of TMGa or TMAl totally input during a δ-doping step. Using heavily carbon δ-doped layers in Al0.3Ga0.7As, a carbon δ-doped pipi doping superlattice possessing a bulk-doped-like hole profile with an average hole density of 1.1×1019 cm−3 is therefore demonstrated as an alternative with unique advantages over other conventional carbon bulk-doping approaches.
Publisher: Wiley
Date: 12-2009
Publisher: The Optical Society
Date: 12-2011
DOI: 10.1364/OE.19.025643
Publisher: SPIE
Date: 09-10-2012
DOI: 10.1117/12.928558
Publisher: Wiley
Date: 14-03-2013
DOI: 10.1002/PIP.2161
Publisher: AIP Publishing
Date: 25-11-2013
DOI: 10.1063/1.4834377
Abstract: Simultaneous growth of ⟨111⟩B free-standing and ±[110] lateral GaAsP epitaxial nanowires on GaAs (001) substrates were observed and investigated by electron microscopy and crystallographic analysis. It was found that the growth of both free-standing and lateral ternary nanowires via Au catalysts was driven by the fact that Au catalysts prefer to maintain low-energy {111}B interfaces with surrounding GaAs(P) materials: in the case of free-standing nanowires, Au catalysts maintain {111}B interfaces with their underlying GaAsP nanowires while in the case of lateral nanowires, each Au catalyst remain their side {111}B interfaces with the surrounding GaAs(P) material during the lateral nanowire growth.
Publisher: AIP Publishing
Date: 11-2000
DOI: 10.1063/1.1314904
Abstract: We have compared the time integrated photoluminescence (PL) and the time resolved PL of several lattice matched InGaAs/InP quantum wells intermixed either by ion implantation or an impurity-free method. We have found that the carrier capture rates into quantum wells and carrier relaxation from the wells depend on the type of intermixing used. Our results indicate that the carrier lifetimes are significantly longer in s les intermixed by the impurity-free methods, while the carrier collection efficiency of the quantum wells is more efficient in s les intermixed by ion implantation.
Publisher: American Chemical Society (ACS)
Date: 08-12-2017
Publisher: American Chemical Society (ACS)
Date: 29-09-2007
DOI: 10.1021/NL071733L
Abstract: Low-temperature time-resolved photoluminescence spectroscopy is used to probe the dynamics of photoexcited carriers in single InP nanowires. At early times after pulsed excitation, the photoluminescence line shape displays a characteristic broadening, consistent with emission from a degenerate, high-density electron-hole plasma. As the electron-hole plasma cools and the carrier density decreases, the emission rapidly converges toward a relatively narrow band consistent with free exciton emission from the InP nanowire. The free excitons in these single InP nanowires exhibit recombination lifetimes closely approaching that measured in a high-quality epilayer, suggesting that in these InP nanowires, electrons and holes are relatively insensitive to surface states. This results in higher quantum efficiencies than other single-nanowire systems as well as significant state-filling and band gap renormalization, which is observed at high electron-hole carrier densities.
Publisher: IOP Publishing
Date: 20-04-2010
Publisher: Wiley
Date: 2000
DOI: 10.1002/1096-9918(200011)29:11<754::AID-SIA924>3.0.CO;2-D
Publisher: Wiley
Date: 10-10-2022
Abstract: Nanoresonators fabricated from low‐loss dielectrics with second‐order nonlinearity have emerged as a widespread platform for nonlinear frequency conversion at the nanoscale. However, a persisting challenge in this research is the generated complex far‐field polarization state of the upconverted light, which is a limiting factor in many applications. It will be highly desirable to generate uniform far‐field polarization states across all propagation directions, to control the polarization truly along the optical axis and to simultaneously be able to tune the polarization along the entire circumference of the Poincaré sphere by solely modifying the excitation polarization. Here, a nonlinear nanoresonator combining all these properties is theoretically proposed and experimentally demonstrated. At first, an analytical model connecting the induced multipolar content of a nanoresonator with a desired far‐field polarization is derived. Based on this, a nonlinear dielectric nanoresonator is designed to enable sum‐frequency generation (SFG) with highly pure and tuneable far‐field polarization states. In the experiment, the nanoresonators fabricated from the III‐V semiconductor gallium arsenide in (110)‐orientation are excited in an SFG scheme with in idually controllable excitation beams. The generation of highly uniform and tuneable far‐field polarization states is demonstrated by combining back‐focal plane measurements with Stokes polarimetry.
Publisher: AIP Publishing
Date: 11-2000
DOI: 10.1063/1.1314907
Abstract: We have recently shown [P. N. K. Deenapanray et al., Appl. Phys. Lett. 77, 626 (2000)] that four electron traps S1(Ec−0.23 eV), S2(Ec−0.46 eV), S3(Ec−0.72 eV), and S4(Ec−0.74 eV) are introduced in rapid thermally-annealed (RTA) SiO2-capped n-type GaAs epitaxial layers. In the present study, we have used deep level transient spectroscopy to investigate the electronic and annealing properties of these deep levels. The electron emission kinetics of S1 is enhanced by an electric field, and the activation energy of S1 decreases linearly from ∼233 to ∼199 meV when the field is increased from 7.5×104 to 13.4×104 V cm−1. The intensities of S1, S2, and S4 show Arrhenius-like dependencies on the RTA temperature, which relate to the outdiffusion of Ga atoms into the SiO2 layer. The intensity of S2(VGa–SiGa) also increases exponentially with the square of the annealing time for RTA at 800 °C. Isochronal annealing experiments show that S1 and S2 are thermally stable below 500 and 400 °C, respectively. S4, which is a member of the EL2 family, is stable up to 600 °C. Secondary defects are introduced during isochronal annealing above 400 °C, and some of these defects are thermally stable at 600 °C.
Publisher: American Chemical Society (ACS)
Date: 18-06-2012
DOI: 10.1021/NL3008083
Abstract: We demonstrate the spin selective coupling of the exciton state with cavity mode in a single quantum dot (QD)-micropillar cavity system. By tuning an external magnetic field, each spin polarized exciton state can be selectively coupled with the cavity mode due to the Zeeman effect. A significant enhancement of spontaneous emission rate of each spin state is achieved, giving rise to a tunable circular polarization degree from -90% to 93%. A four-level rate equation model is developed, and it agrees well with our experimental data. In addition, the coupling between photon mode and each exciton spin state is also achieved by varying temperature, demonstrating the full manipulation over the spin states in the QD-cavity system. Our results pave the way for the realization of future quantum light sources and the quantum information processing applications.
Publisher: IOP Publishing
Date: 14-08-2018
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2011
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2004
Publisher: AIP Publishing
Date: 06-2006
DOI: 10.1063/1.2197038
Abstract: Plan-view and cross-sectional transmission electron microscopy have been used for a detailed study of the defects formed in capped InAs∕GaAs quantum dot (QD) s les. Three main types of defects, V-shaped defects, single stacking faults, and stacking fault pyramids, were found to form under growth conditions that led to either very large, indium enriched, or coalesced islands. All three types of defects originate at the buried quantum dot layer and then travel through the GaAs cap to the surface on the {111} planes. The V-shaped defects were the most common and typically consisted of two pairs of closely spaced 60° Shockley partials with a ⟨211⟩ line direction. The two pairs originate together at the buried QD layer and then travel in “opposite” directions on different {111} planes. The second type of defect is the single stacking fault which consists of a single pair of partial dislocations separated by an ≈50nm wide stacking fault. Finally, both complete and incomplete stacking fault pyramids were observed. In the case of the complete stacking fault pyramid the bounding dislocations along the [110], [11¯0], [101¯], and [101] directions were identified as stair rods. A possible mechanism for the stacking fault pyramid formation, which can also account for the creation of incomplete stacking fault pyramids, is presented.
Publisher: AIP Publishing
Date: 06-12-2004
DOI: 10.1063/1.1833563
Abstract: The effects of thermal annealing on C-doped InGaAs∕AlGaAs quantum well laser structures capped with titanium dioxide (TiO2) layers were investigated. The atomic interdiffusion was greatly suppressed by the presence of a TiO2 capping layer during annealing, inhibiting even the thermal intermixing observed in the uncapped s le. An increase in the amount of lattice contraction associated with the presence of substitutional carbon CAs after annealing without a capping layer was observed, but not after annealing with a TiO2 capping layer. Capacitance–voltage measurements confirmed the electrical activation of carbon after annealing without a dielectric layer and show a negligible change after annealing using a TiO2 capping layer. The possible mechanisms involving both the atomic intermixing on the group III sublattice and carbon activation on the group V sublattice and the implications for optoelectronic device integration using impurity-free intermixing are discussed.
Publisher: IOP Publishing
Date: 14-03-2008
Publisher: IEEE
Date: 09-2006
Publisher: Springer Science and Business Media LLC
Date: 15-10-2015
DOI: 10.1038/SREP15339
Abstract: We propose the optical design for the absorptive element of photodetectors to achieve wavelength selective photo response based on resonant guided modes supported in semiconductor nanowires. We show that the waveguiding properties of nanowires result in very high absorption efficiency that can be exploited to reduce the volume of active semiconductor compared to planar photodetectors, without compromising the photocurrent. We present a design based on a group of nanowires with varying diameter for multi-color photodetectors with small footprint. We discuss the effect of a dielectric shell around the nanowires on the absorption efficiency and present a simple approach to optimize the nanowire diameter-dielectric shell thickness for maximizing the absorption efficiency.
Publisher: AIP Publishing
Date: 26-02-2007
DOI: 10.1063/1.2710006
Abstract: The effect of high temperature annealing of the InAs∕InP quantum dots (QDs) containing a thin GaAs interlayer is investigated. The QDs are rapid thermally annealed at 750, 800, 850, and 900°C for 30s. The QDs with the GaAs interlayer show good thermal stability up to 850°C as well as enhanced integrated photoluminescence (PL) intensity and reduced PL linewidth. The effect of high energy (450keV) phosphorous ion implantation at room temperature with doses of 5×1011–5×1013ions∕cm2 with subsequent high temperature (750–850°C) rapid thermal annealing is also studied. A large implantation-induced energy shift of up to 309meV (400nm) is observed. The implanted s les annealed at 850°C show reduced PL linewidth and enhanced integrated PL intensity compared to the implanted s les annealed at 750°C.
Publisher: AIP Publishing
Date: 02-1998
DOI: 10.1063/1.366830
Abstract: Enhancement of interdiffusion in GaAs/AlGaAs quantum wells due to anodic oxides was studied. Photoluminescence, transmission electron microscopy, and quantum well modeling were used to understand the effects of intermixing on the quantum well shape. Residual water in the oxide was found to increase the intermixing, though it was not the prime cause for intermixing. Injection of defects such as group III vacancies or interstitials was considered to be a driving force for the intermixing. Different current densities used in the experimental range to create anodic oxides had little effect on the intermixing.
Publisher: AIP Publishing
Date: 29-05-2006
DOI: 10.1063/1.2208371
Abstract: Proton implantation-induced intermixing of InAs quantum dots (QDs) capped with InP, GaInAsP, and InP and InGaAs layers grown by metal-organic chemical vapor deposition is investigated. The s les are annealed at 750, 800, 850, and 900°C for 30s and thermal stability of the QDs is studied. The optimum annealing temperature is around 800°C which gives maximum implantation-induced energy shift. The QDs capped with InP layers show the highest implantation-induced energy shift due to strong group V interdiffusion whereas the QDs grown on and capped with GaInAsP layers show the least implantation-induced energy shift due to weak group V and group III interdiffusion. The QDs capped with InP and InGaAs layers show intermediate implantation-induced energy shift and are less thermally stable compared to the QDs grown on and capped with GaInAsP layers. The QDs capped with InP layers show enhanced photoluminescence (PL) intensity when implanted with lower proton dose (less than 5×1014ions∕cm2). On the other hand higher proton dose (more than 1×1014ions∕cm2) reduces the PL linewidth in all s les.
Publisher: IOP Publishing
Date: 17-10-2017
Abstract: We compare the characteristics of phase-pure MOCVD grown ZB and WZ InAs nanowire transistors in several atmospheres: air, dry pure N
Publisher: SPIE
Date: 29-03-2002
DOI: 10.1117/12.460800
Publisher: AIP Publishing
Date: 18-09-2002
DOI: 10.1063/1.1503857
Abstract: In this work, different dielectric caps were deposited on the GaAs/AlGaAs quantum well (QW) structures followed by rapid thermal annealing to generate different degrees of interdiffusion. Deposition of a layer of GaxOy on top of these dielectric caps resulted in significant suppression of interdiffusion. In these s les, it was found that although the deposition of GaxOy and subsequent annealing caused additional injection of Ga into the SiO2 layer, Ga atoms were still able to outdiffuse from the GaAs QW structure during annealing, to generate excess Ga vacancies. The suppression of interdiffusion with the presence of Ga vacancies was explained by the thermal stress effect which suppressed Ga vacancy diffusion during annealing. It suggests that GaxOy may therefore be used as a mask material in conjunction with other dielectric capping layers in order to control and selectively achieve impurity-free vacancy disordering.
Publisher: IOP Publishing
Date: 18-03-2010
Publisher: Elsevier BV
Date: 12-1998
Publisher: AIP Publishing
Date: 15-02-2010
DOI: 10.1063/1.3309748
Abstract: In this article, we optimize the coupling efficiency from a GaAs microdisk resonator into a single mode spiral waveguide. A classical microdisk resonator coupling light into a nonevanescent straight waveguide reaches a typical coupling efficiency of 67%. We show that the introduction of a spiral waveguide that works both as a waveguide and circular Bragg reflector can improve such efficiency to almost 90%. The same structure with the addition of a taper can couple up to 80% of the generated power into a slot waveguide.
Publisher: American Chemical Society (ACS)
Date: 05-10-2012
DOI: 10.1021/NL303028U
Abstract: We report the epitaxial growth of defect-free zinc-blende structured InAs nanowires on GaAs{111}(B) substrates using palladium catalysts in a metal-organic chemical vapor deposition reactor. Through detailed morphological, structural, and chemical characterizations using electron microscopy, it is found that these defect-free InAs nanowires grew along the directions with four low-energy {111} faceted side walls and {1[combining overline]1[combining overline]3[combining overline]} nanowire/catalyst interfaces. It is anticipated that these defect-free nanowires benefit from the fact that the nanowire/catalyst interfaces does not contain the {111} planes, and the nanowire growth direction is not along the directions. This study provides an effective approach to control the crystal structure and quality of epitaxial III-V nanowires.
Publisher: AIP Publishing
Date: 17-11-2008
DOI: 10.1063/1.3033551
Abstract: The structural and morphological characteristics of InAs/GaAs radial nanowire heterostructures were investigated using transmission electron microscopy. It has been found that the radial growth of InAs was preferentially initiated on the {112}A sidewalls of GaAs nanowires. This preferential deposition leads to extraordinarily asymmetric InAs/GaAs radial nanowire heterostructures. Such formation of radial nanowire heterostructures provides an opportunity to engineer hierarchical nanostructures, which further widens the potential applications of semiconductor nanostructures.
Publisher: SPIE
Date: 22-09-2006
DOI: 10.1117/12.692715
Publisher: IEEE
Date: 12-2010
Publisher: IOP Publishing
Date: 06-10-2008
Publisher: American Chemical Society (ACS)
Date: 03-09-2013
DOI: 10.1021/NL402180K
Abstract: Quantitative mechanical testing of single-crystal GaAs nanowires was conducted using in situ deformation transmission electron microscopy. Both zinc-blende and wurtzite structured GaAs nanowires showed essentially elastic deformation until bending failure associated with buckling occurred. These nanowires fail at compressive stresses of ~5.4 GPa and 6.2 GPa, respectively, which are close to those values calculated by molecular dynamics simulations. Interestingly, wurtzite nanowires with a high density of stacking faults fail at a very high compressive stress of ~9.0 GPa, demonstrating that the nanowires can be strengthened through defect engineering. The reasons for the observed phenomenon are discussed.
Publisher: AIP Publishing
Date: 02-02-2015
DOI: 10.1063/1.4907348
Abstract: Reduced quantum dot (QD) absorption due to state filling effects and enhanced electron transport in doped QDs are demonstrated to play a key role in solar energy conversion. Reduced QD state absorption with increased n-doping is observed in the self-assembled In0.5Ga0.5As/GaAs QDs from high resolution below-bandgap external quantum efficiency (EQE) measurement, which is a direct consequence of the Pauli exclusion principle. We also show that besides partial filling of the quantum states, electron-doping produces negatively charged QDs that exert a repulsive Coulomb force on the mobile electrons, thus altering the electron trajectory and reducing the probability of electron capture, leading to an improved collection efficiency of photo-generated carriers, as indicated by an absolute above-bandgap EQE measurement. The resulting redistribution of the mobile electron in the planar direction is further validated by the observed photoluminescence intensity dependence on doping.
Publisher: IEEE
Date: 12-2006
Publisher: AIP Publishing
Date: 18-10-2004
DOI: 10.1063/1.1808235
Abstract: We have used ion implantation for erbium doping of mesoporous silicon microcavities. Optically active erbium-doped microcavities with Q factors in excess of 1500 have been demonstrated. We observed strong modification of the emission properties of the erbium in the microcavity with an accompanying cavity enhancement factor of 25. In addition, power- and temperature-dependent photoluminescence measurements indicate that erbium-implanted porous silicon has excitation mechanism very similar to that of erbium in a crystalline silicon host.
Publisher: IEEE
Date: 12-2010
Publisher: IEEE
Date: 12-2010
Publisher: IOP Publishing
Date: 17-03-2006
Publisher: American Chemical Society (ACS)
Date: 29-06-2012
DOI: 10.1021/NN300962Z
Abstract: The doping-dependent photoconductive properties of in idual GaAs nanowires have been studied by conductive atomic force microscopy. Linear responsivity against the bias voltage is observed for moderate n-doped GaAs wires with a Schottky contact under illumination, while that of the undoped ones exhibits a saturated response. The carrier lifetime of a single nanowire can be obtained by simulating the characteristic photoelectric behavior. Consistent with the photoluminescence results, the significant drop of minority hole lifetime, from several hundred to subpicoseconds induced by n-type doping, leads to the distinct photoconductive features. Moreover, by comparing with the photoelectric behavior of AlGaAs shelled nanowires, the equivalent recombination rate of carriers at the surface is assessed to be >1 × 10(12) s(-1) for 2 × 10(17)cm(-3) n-doped bare nanowires, nearly 30 times higher than that of the doping-related bulk effects. This work suggests that intentional doping in nanowires could change the charge status of the surface states and impose significant impact on the electrical and photoelectrical performances of semiconductor nanostructures.
Publisher: IOP Publishing
Date: 17-03-2006
Publisher: IOP Publishing
Date: 08-11-2011
DOI: 10.1088/0022-3727/44/47/475105
Abstract: In this work, proton and arsenic ion implantation induced intermixing in AlInGaAs/InGaAs quantum wells (QWs) has been studied and compared with InGaAsP/InGaAs QWs. The different interdiffusion results obtained from the two QW structures are compared and discussed based on thermal annealing studies, different implantation ion species, dynamic annealing effects of barrier layers, as well as interdiffusion mechanisms.
Publisher: The Optical Society
Date: 06-1999
Publisher: AIP Publishing
Date: 06-2006
DOI: 10.1063/1.2202704
Abstract: In this work, rapid thermal annealing was performed on InGaAs∕GaAs quantum dot infrared photodetectors (QDIPs) at different temperatures. The photoluminescence showed a blueshifted spectrum in comparison with the as-grown s le when the annealing temperature was higher than 700°C, as a result of thermal interdiffusion of the quantum dots (QDs). Correspondingly, the spectral response from the annealed QDIP exhibited a redshift. At the higher annealing temperature of 800°C, in addition to the largely redshifted photoresponse peak of 7.4μm (compared with the 6.1μm of the as-grown QDIP), a high energy peak at 5.6μm (220meV) was also observed, leading to a broad spectrum linewidth of 40%. This is due to the large interdiffusion effect which could greatly vary the composition of the QDs and thus increase the relative optical absorption intensity at higher energy. The other important detector characteristics such as dark current, peak responsivity, and detectivity were also measured. It was found that the overall device performance was not affected by low annealing temperature, however, for high annealing temperature, some degradation in device detectivity (but not responsivity) was observed. This is a consequence of increased dark current due to defect formation and increased ground state energy.
Publisher: AIP Publishing
Date: 26-12-2011
DOI: 10.1063/1.3671367
Abstract: We use spatially and temporally resolved photoluminescence to measure exciton diffusion in single zinc blende GaAs/AlGaAs core/shell and mixed phase InP nanowires. Excitons in the single phase GaAs/AlGaAs nanowires are seen to diffuse rapidly throughout the nanowire with a measured diffusion constant ranging from 45 to 100 cm2/s, while in the mixed phase, InP nanowire electrons and holes are seen to rapidly localize to the quantum confined states in the zinc blende and wurtzite segments, respectively. The diffusion constant in the GaAs/AlGaAs nanowire is similar to the best hole mobilities observed in modulation doped heterostructures.
Publisher: AIP Publishing
Date: 12-2012
DOI: 10.1063/1.4768283
Abstract: Various approaches can be used to selectively control the amount of intermixing in III-V quantum well and quantum dot structures. Impurity-free vacancy disordering is one technique that is favored for its simplicity, however this mechanism is sensitive to many experimental parameters. In this study, a series of silicon oxynitride capping layers have been used in the intermixing of InGaAs/GaAs quantum well and quantum dot structures. These thin films were deposited by sputter deposition in order to minimize the incorporation of hydrogen, which has been reported to influence impurity-free vacancy disordering. The degree of intermixing was probed by photoluminescence spectroscopy and this is discussed with respect to the properties of the SiOxNy films. This work was also designed to monitor any additional intermixing that might be attributed to the sputtering process. In addition, the high-temperature stress is known to affect the group-III vacancy concentration, which is central to the intermixing process. This stress was directly measured and the experimental values are compared with an elastic-deformation model.
Publisher: AIP Publishing
Date: 15-03-2000
DOI: 10.1063/1.372248
Abstract: Visible and ultraviolet micro-Raman scattering was employed to monitor the high-pressure high-temperature annealing of Mg/P-implanted GaN films. The results illustrate the use of Raman scattering to monitor processing of GaN where fast feedback is required. Temperatures up to 1500 °C with nitrogen overpressures of 1–1.5 GPa were used during the annealing. The crystalline quality, the strain, and the free carrier concentration in the ion-implanted GaN films was monitored, averaged over the layer thickness and in a 40-nm-thin surface layer of the s le. Annealing temperatures of 1400–1500 °C were found to result in the nearly full recovery of the crystalline quality of ion-implanted GaN. No significant surface degradation occurred during the annealing. High nitrogen overpressures proved very effective in preventing the nitrogen out-diffusion from the GaN surface at high temperatures. Strain was introduced during the annealing. Changes in the free carrier concentration were studied.
Publisher: Elsevier BV
Date: 04-2008
Publisher: Optica Publishing Group
Date: 24-06-2009
Publisher: OSA
Date: 2017
Publisher: American Chemical Society (ACS)
Date: 21-05-2018
DOI: 10.1021/ACS.NANOLETT.8B00334
Abstract: Semiconductor nanowire (NW) lasers have attracted considerable research effort given their excellent promise for nanoscale photonic sources. However, NW lasers currently exhibit poor directionality and high threshold gain, issues critically limiting their prospects for on-chip light sources with extremely reduced footprint and efficient power consumption. Here, we propose a new design and experimentally demonstrate a vertically emitting indium phosphide (InP) NW laser structure showing high emission directionality and reduced energy requirements for operation. The structure of the laser combines an InP NW integrated in a cat's eye (CE) antenna. Thanks to the antenna guidance with broken asymmetry, strong focusing ability, and high Q-factor, the designed InP CE-NW lasers exhibit a higher degree of polarization, narrower emission angle, enhanced internal quantum efficiency, and reduced lasing threshold. Hence, this NW laser-antenna system provides a very promising approach toward the achievement of high-performance nanoscale lasers, with excellent prospects for use as highly localized light sources in present and future integrated nanophotonics systems for applications in advanced sensing, high-resolution imaging, and quantum communications.
Publisher: SPIE
Date: 17-09-1998
DOI: 10.1117/12.321942
Publisher: IEEE
Date: 2005
Publisher: AIP Publishing
Date: 20-11-2000
DOI: 10.1063/1.1328047
Abstract: Wurtzite GaN films grown on sapphire substrates are studied by nanoindentation with a spherical indenter. No systematic dependence of the mechanical properties of GaN epilayers on the film thickness (at least for thicknesses from 1.8 to 4 μm) as well as on doping type is observed. Slip is identified as one of the physical mechanisms responsible for plastic deformation of GaN and may also contribute to the “pop-in” events observed during loading. No visible material cracking is found even after indentations at high loads (900 mN), but a pronounced elevation of the material surrounding the impression is observed.
Publisher: IEEE
Date: 12-2012
Publisher: AIP Publishing
Date: 28-03-2003
DOI: 10.1063/1.1555273
Abstract: We have investigated the effect of implantation at room temperature and 200 °C into lattice matched InP/InGaAs quantum well structures capped with InP and InGaAs layers. P− ions of 20 keV were implanted into the cap layer at doses of 1×1012−1×1014 cm−2. The dose dependent evolution of shifts in photoluminescence energy for the InP capped s le was found to be affected by the implant temperature. Rutherford back scattering measurements show that the nature of the damage induced at different implant temperatures is responsible for this behavior. It was found that the InGaAs capped s le was less sensitive to the implant temperature than the InP capped s le.
Publisher: American Chemical Society (ACS)
Date: 27-02-2015
DOI: 10.1021/NL5046878
Abstract: We use low-temperature photoluminescence, photoluminescence excitation, and photoluminescence imaging spectroscopy to explore the optical and electronic properties of GaAs/AlGaAs quantum well tube (QWT) heterostructured nanowires (NWs). We find that GaAs QWTs with widths >5 nm have electronic states which are delocalized and continuous along the length of the NW. As the NW QWT width decreases from 5 to 1.5 nm, only a single electron state is bound to the well, and no optical excitations to a confined excited state are present. Simultaneously, narrow emission lines (fwhm < 600 μeV) appear which are localized to single spatial points along the length of the NW. We find that these quantum-dot-like states broaden at higher temperatures and quench at temperatures above 80 K. The lifetimes of these localized states are observed to vary from dot to dot from 160 to 400 ps. The presence of delocalized states and then localized states as the QWTs become more confined suggests both opportunities and challenges for possible incorporation into quantum-confined device structures.
Publisher: IEEE
Date: 12-2012
Publisher: AIP Publishing
Date: 11-1996
DOI: 10.1063/1.363546
Abstract: Effects of anodic oxide induced intermixing on the structural and optical properties of stacked GaAs quantum wire (QWR) structures grown on a sawtooth-type nonplanar GaAs substrate are investigated. Cross-sectional transmission electron microscope (XTEM) observation, temperature dependent photoluminescence (PL) and cathodoluminescence (CL) imaging were used. Intermixing was achieved by pulsed anodic oxidation of the GaAs cap layer and subsequent rapid thermal annealing, was verified by XTEM analysis. A significant enhancement of QWR PL is observed accompanied by a notable blueshift of the sidewall quantum well (SQWL) PL due to the intermixing. Furthermore, an extended necking region is observed after the intermixing by spatially resolved CL. The temperature dependence of the PL intensities of both SQWL and QWR show maxima at approximately T∼110 K indicating the role of the extended necking region in feeding carriers to SQWL and QWR.
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.ULTRAMIC.2013.02.012
Abstract: Controllable doping of semiconductor nanowires is critical to realize their proposed applications, however precise and reliable characterization of dopant distributions remains challenging. In this article, we demonstrate an atomic-resolution three-dimensional elemental mapping of pristine semiconductor nanowires on growth substrates by using atom probe tomography to tackle this major challenge. This highly transferrable method is able to analyze the full diameter of a nanowire, with a depth resolution better than 0.17 nm thanks to an advanced reconstruction method exploiting the specimen's crystallography, and an enhanced chemical sensitivity of better than 8-fold increase in the signal-to-noise ratio.
Publisher: IEEE
Date: 12-2010
Publisher: Optica Publishing Group
Date: 16-09-2009
DOI: 10.1364/OE.17.017570
Publisher: EDP Sciences
Date: 29-11-2003
Publisher: IEEE
Date: 12-2010
Publisher: Wiley
Date: 04-11-2014
Publisher: American Chemical Society (ACS)
Date: 13-09-2012
DOI: 10.1021/NL3026828
Abstract: Using transient terahertz photoconductivity measurements, we have made noncontact, room temperature measurements of the ultrafast charge carrier dynamics in InP nanowires. InP nanowires exhibited a very long photoconductivity lifetime of over 1 ns, and carrier lifetimes were remarkably insensitive to surface states despite the large nanowire surface area-to-volume ratio. An exceptionally low surface recombination velocity (170 cm/s) was recorded at room temperature. These results suggest that InP nanowires are prime candidates for optoelectronic devices, particularly photovoltaic devices, without the need for surface passivation. We found that the carrier mobility is not limited by nanowire diameter but is strongly limited by the presence of planar crystallographic defects such as stacking faults in these predominantly wurtzite nanowires. These findings show the great potential of very narrow InP nanowires for electronic devices but indicate that improvements in the crystallographic uniformity of InP nanowires will be critical for future nanowire device engineering.
Publisher: IEEE
Date: 12-2012
Publisher: AIP Publishing
Date: 07-07-2008
DOI: 10.1063/1.2955517
Abstract: We report the postgrowth fabrication of two-color InGaAs∕GaAs quantum dot infrared photodetectors (QDIPs). By capping half of the as-grown QDIP structure with titanium dioxide (TiO2) and performing rapid thermal annealing under the optimized condition, a blueshifted photoluminescence from the uncapped region was obtained compared with the TiO2 covered region. The corresponding device spectral photoresponse from the two adjacent regions exhibited a shift of 0.8μm around the wavelength of 6μm. This is a result of the simultaneous promotion and suppression of thermal interdiffusion during rapid thermal annealing.
Publisher: AIP Publishing
Date: 26-06-2003
DOI: 10.1063/1.1576516
Abstract: MeV P+ implanted and annealed p-InP, and Fe+ implanted and annealed semi-insulating InP have both been shown to produce the high resistivity, good mobility, and ultrafast optical response desired for ultrafast photodetectors. Hall effect measurements and time resolved photoluminescence were used to analyze the electrical and optical features of such implanted materials. Low temperature annealing was found to yield the fastest response times—130 fs for Fe+ implanted and 400 fs for P+ implanted InP, as well as resistivities of the order ∼106 Ω/square. It was found that the electrical activation of Fe-related centers, useful for achieving high resistivities in Fe+ implanted semi-insulating InP, was not fully realized at the annealing temperatures chosen to produce the fastest optical response. Implanting p-InP in the dose regime where type conversion occurs, and subsequent annealing at 500 °C, produces high resistivities and ultrafast carrier trapping times that are only marginally dose dependent.
Publisher: IOP Publishing
Date: 07-05-2009
Publisher: AIP Publishing
Date: 02-2010
DOI: 10.1063/1.3300836
Abstract: Photoluminescence measurements have been used to investigate the optically active defect centers formed by silicon implantation and a subsequent anneal at 275, 400, or 525 °C. The presence of boron in p-type silicon is found to produce deleterious effects on the luminescence of the interstitial-related W- and X-centers as well as a lower energy broad luminescence band. This effect has not been previously reported but it is consistent with the suppression of interstitial-related {311} extended defect formation in the presence of high boron concentrations at higher annealing temperatures. The results presented in this letter provide insight into the role of boron in the initial stages of interstitial cluster formation.
Publisher: Wiley
Date: 19-11-2012
Publisher: AIP Publishing
Date: 24-12-2007
DOI: 10.1063/1.2828034
Abstract: We use polarization-resolved and temperature-dependent photoluminescence of single zincblende (ZB) (cubic) and wurtzite (WZ) (hexagonal) InP nanowires to probe differences in selection rules and bandgaps between these two semiconductor nanostructures. The WZ nanowires exhibit a bandgap 80meV higher in energy than the ZB nanowires. The temperature dependence of the PL is similar but not identical for the WZ and ZB nanowires. We find that ZB nanowires exhibit strong polarization parallel to the nanowire axis, while the WZ nanowires exhibit polarized emission perpendicular to the nanowire axis. This behavior is interpreted in terms of the different selection rules for WZ and ZB crystal structures.
Publisher: American Chemical Society (ACS)
Date: 31-10-2016
DOI: 10.1021/ACS.NANOLETT.6B03525
Abstract: The quest for nanoscale light sources with designer radiation patterns and polarization has motivated the development of nanoantennas that interact strongly with the incoming light and are able to transform its frequency, radiation, and polarization patterns. Here, we demonstrate dielectric AlGaAs nanoantennas for efficient second harmonic generation, enabling the control of both directionality and polarization of nonlinear emission. This is enabled by specialized III-V semiconductor nanofabrication of high-quality AlGaAs nanostructures embedded in optically transparent low-index material, thus allowing for simultaneous forward and backward nonlinear emission. We show that the nanodisk AlGaAs antennas can emit second harmonic in preferential direction with a backward-to-forward ratio of up to five and can also generate complex vector polarization beams, including beams with radial polarization.
Publisher: AIP Publishing
Date: 28-10-2002
DOI: 10.1063/1.1519728
Abstract: We have used capacitance–voltage and deep level transient spectroscopy techniques to study the relocation of impurities, such as Zn and Cu, in impurity-free disordered (IFD) p-type GaAs. A four-fold increase in the doping concentration is observed after annealing at 925 °C. Two electrically active defects HA (EV+0.39 eV) and HB2 (EV+0.54 eV), which we have attributed to Cu- and Asi/AsGa-related levels, respectively, are observed in the disordered p-GaAs layers. The injection of gallium vacancies causes segregation of Zn dopant atoms and Cu towards the surface of IFD s les. The atomic relocation process is critically assessed in terms of the application of IFD to the band gap engineering of doped GaAs-based heterostructures.
Publisher: SPIE
Date: 28-08-2008
DOI: 10.1117/12.793558
Publisher: AIP Publishing
Date: 13-08-2007
DOI: 10.1063/1.2770765
Abstract: The effect of GaP strain compensation layers was investigated on ten-layer InGaAs∕GaAs quantum dot infrared photodetectors (QDIPs) grown by metal-organic chemical-vapor deposition. Compared with the normal QDIP structure, the insertion of GaP has led to a narrowed spectral linewidth and slightly improved detector performance. A more significant influence of GaP was observed after the structure was annealed at various temperatures. While a similar amount of wavelength tuning was obtained, the GaP QDIPs exhibited much less degradation in device characteristics with increasing annealing temperature.
Publisher: American Chemical Society (ACS)
Date: 06-06-2016
DOI: 10.1021/ACS.NANOLETT.6B01461
Abstract: Selective-area epitaxy is highly successful in producing application-ready size-homogeneous arrays of III-V nanowires without the need to use metal catalysts. Previous works have demonstrated excellent control of nanowire properties but the growth mechanisms remain rather unclear. Herein, we report a detailed growth study revealing that fundamental growth mechanisms of pure wurtzite InP ⟨111⟩A nanowires can indeed differ significantly from the simple picture of a facet-limited selective-area growth process. A dual growth regime with and without metallic droplet is found to coexist under the same growth conditions for different diameter nanowires. Incubation times and highly nonmonotonous growth rate behaviors are revealed and explained within a dedicated kinetic model.
Publisher: Wiley
Date: 02-07-2018
Publisher: American Chemical Society (ACS)
Date: 03-04-2015
DOI: 10.1021/NL504929N
Abstract: We report an analysis method that combines microphotoluminescence mapping and lifetime mapping data of single semiconductor nanowires to extract the doping concentration, nonradiative lifetime, and internal quantum efficiency along the length of the nanowires. Using this method, the doping concentration of single Si-doped wurtzite InP nanowires are mapped out and confirmed by the electrical measurements of single nanowire devices. Our method has important implication for single nanowire detectors and LEDs and nanowire solar cells applications.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2011
Publisher: IOP Publishing
Date: 05-08-2010
DOI: 10.1088/0022-3727/43/33/335104
Abstract: Modern technology is heavily reliant on silicon dioxide and silicon nitride thin films. These films have many electronic and optical applications, and in some cases silicon oxynitride films of intermediate composition are desirable. We have systematically deposited several SiO x N y films by magnetron sputter deposition and thoroughly investigated their composition with Rutherford backscattering spectrometry and optical measurements. The as-deposited stress in these thin films was also measured and all were found to be compressive. Temperature-dependent stress measurements up to 450 ° C were then used to extract the biaxial modulus and coefficient of thermal expansion for each SiO x N y . The SiO 2 -like films exhibit negative thermal expansion, which is consistent with a strong but porous structure. Increasing the nitrogen content results in the thermal expansion coefficient increasing towards values reported elsewhere for Si 3 N 4 .
Publisher: The Electrochemical Society
Date: 1999
DOI: 10.1149/1.1391000
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9NA00479C
Abstract: For nanowire lasers, end-facets matter a rigorous statistical study demonstrates that short ultrasound or PDMA transfer provides optimized lasing performance.
Publisher: Springer Science and Business Media LLC
Date: 03-2008
Publisher: SPIE
Date: 15-12-2000
DOI: 10.1117/12.409876
Publisher: Springer Science and Business Media LLC
Date: 07-04-2007
Publisher: American Chemical Society (ACS)
Date: 26-09-2014
DOI: 10.1021/NL503043P
Abstract: Achieving bulk-like charge carrier mobilities in semiconductor nanowires is a major challenge facing the development of nanowire-based electronic devices. Here we demonstrate that engineering the GaAs nanowire surface by overcoating with optimized AlGaAs shells is an effective means of obtaining exceptionally high carrier mobilities and lifetimes. We performed measurements of GaAs/AlGaAs core-shell nanowires using optical pump-terahertz probe spectroscopy: a noncontact and accurate probe of carrier transport on ultrafast time scales. The carrier lifetimes and mobilities both improved significantly with increasing AlGaAs shell thickness. Remarkably, optimized GaAs/AlGaAs core-shell nanowires exhibited electron mobilities up to 3000 cm(2) V(-1) s(-1), reaching over 65% of the electron mobility typical of high quality undoped bulk GaAs at equivalent photoexcited carrier densities. This points to the high interface quality and the very low levels of ionized impurities and lattice defects in these nanowires. The improvements in mobility were concomitant with drastic improvements in photoconductivity lifetime, reaching 1.6 ns. Comparison of photoconductivity and photoluminescence dynamics indicates that midgap GaAs surface states, and consequently surface band-bending and depletion, are effectively eliminated in these high quality heterostructures.
Publisher: Springer Science and Business Media LLC
Date: 12-12-2013
DOI: 10.1038/NCOMMS3949
Abstract: Metamaterials, artificial electromagnetic media realized by subwavelength nano-structuring, have become a paradigm for engineering electromagnetic space, allowing for independent control of both electric and magnetic responses of the material. Whereas most metamaterials studied so far are limited to passive structures, the need for active metamaterials is rapidly growing. However, the fundamental question on how the energy of emitters is distributed between both (electric and magnetic) interaction channels of the metamaterial still remains open. Here we study simultaneous spontaneous emission of quantum dots into both of these channels and define the control parameters for tailoring the quantum-dot coupling to metamaterials. By superimposing two orthogonal modes of equal strength at the wavelength of quantum-dot photoluminescence, we demonstrate a sharp difference in their interaction with the magnetic and electric metamaterial modes. Our observations reveal the importance of mode engineering for spontaneous emission control in metamaterials, paving a way towards loss-compensated metamaterials and metamaterial nanolasers.
Publisher: IEEE
Date: 2006
Publisher: Institution of Engineering and Technology (IET)
Date: 20-07-1995
DOI: 10.1049/EL:19950876
Publisher: AIP Publishing
Date: 23-07-2018
DOI: 10.1063/1.5027763
Abstract: Understanding the band structure evolution of (AlxGa1−x)2O3 alloys is of fundamental importance for developing Ga2O3-based power electronic devices and vacuum ultraviolet super-radiation hard detectors. Here, we report on the bandgap engineering of β-(AlxGa1−x)2O3 thin films and the identification of compositionally dependent electronic band structures by a combination of absorption spectra analyses and density functional theory calculations. Single-monoclinic β-phase (AlxGa1−x)2O3 (0 ≤ x ≤ 0.54) films with a preferred (−201) orientation were grown by laser molecular beam epitaxy with tunable bandgap ranging from 4.5 to 5.5 eV. The excellent fitting of absorption spectra by the relation of (αhν)1/2 ∝ (hν-E) unambiguously identifies that β-(AlxGa1−x)2O3 alloys are indirect bandgap semiconductors. Theoretical calculations predict that the indirect nature of β-(AlxGa1−x)2O3 becomes more pronounced with increased Al composition due to the increased eigenvalue energy gap between M and Г points in the valence band. The experimentally determined indirect bandgap exhibits almost a linear relationship with Al composition, which is consistent with the theoretical calculation and indicates a small bowing effect and a good miscibility. The identification and modulation of (AlxGa1−x)2O3 band structures allows rational design of ultra-wide bandgap oxide heterostructures for the applications in power electronics and solar-blind or X-ray detection.
Publisher: The Optical Society
Date: 08-08-2011
DOI: 10.1364/OE.19.016058
Publisher: IEEE
Date: 02-2008
Publisher: IEEE
Date: 2000
Publisher: AIP Publishing
Date: 20-10-2023
DOI: 10.1063/5.0168186
Publisher: IEEE
Date: 07-2006
Publisher: IOP Publishing
Date: 13-05-2009
DOI: 10.1088/0957-4484/20/22/225606
Abstract: InP nanowires were grown on 111B InP substrates by metal-organic chemical vapour deposition in the presence of colloidal gold particles as catalysts. Transmission electron microscopy and photoluminescence measurements were carried out to investigate the effects of V/III ratio and nanowire diameter on structural and optical properties. Results show that InP nanowires grow preferably in the wurtzite crystal structure than the zinc blende crystal structure with increasing V/III ratio or decreasing diameter. Additionally, time-resolved photoluminescence (TRPL) studies have revealed that wurtzite nanowires show longer recombination lifetimes of approximately 2500 ps with notably higher quantum efficiencies.
Publisher: American Vacuum Society
Date: 2003
DOI: 10.1116/1.1535927
Abstract: The effect of stress on defect creation and diffusion during impurity-free disordering of SiOx-capped n-GaAs epitaxial layers has been investigated using deep level transient spectroscopy. The oxygen content in the SiOx layer and the nature of the stress that it imposes on the GaAs layer were varied by changing the nitrous oxide flow rate, N, during plasma-enhanced chemical vapor deposition of the capping layer. The peak intensity of defects S1 and S4 increased with the increasing nitrous oxide flow rate to exhibit a maximum in the range 80 sccm& N& sccm. Any further increase in N resulted in a decrease in peak defect intensity, which reached an almost constant value for N& sccm. On the other hand, the peak intensity of S2* increased linearly with N. We have explained the maximum in the intensity of defects S1 and S4 for 80 sccm& N& sccm to be due to a corresponding maximum in the compressive stress which is experienced by the capped GaAs layer during annealing. Although the creation of S2*, which we have proposed to be a complex involving the gallium vacancy (VGa), is enhanced with the increasing compressive stress, it also becomes efficiently converted into the arsenic-antisite, AsGa. The compound effect of these opposing mechanisms results in a linear dependence of the peak intensity of S2* on N. This study is to the best of our knowledge the first to provide the evidence for the stress-dependent anti-correlation between VGa- and AsGa-related defects in GaAs. We have also narrowed the origin of S1 to complexes involving arsenic interstitials, Asi, and/or AsGa.
Publisher: IEEE
Date: 12-2013
Publisher: IEEE
Date: 09-2012
Publisher: AIP Publishing
Date: 31-10-2003
DOI: 10.1063/1.1619567
Abstract: A study of the evolution of sheet resistance of p- and n-type In0.53Ga0.47As epilayers during O, C, Li, and H irradiation was conducted. The threshold dose at which the material becomes highly resistive increased upon decreasing the mass of the implanted ion, was higher for n-InGaAs as compared to p-InGaAs and was greater for s les with a higher initial free carrier concentration. Implantation with H+ yielded isolation behavior that was different from that for implantation with the three medium-mass ions. The thermal stability of defects induced by implantation was also investigated by cumulative annealing, and was found to be slightly higher in n-InGaAs as compared to p-InGaAs. Shallow donor production in the InGaAs epilayer during implantation played a crucial role in determining the electrical characteristics of the s les.
Publisher: IEEE
Date: 09-2010
Publisher: AIP Publishing
Date: 15-02-2006
DOI: 10.1063/1.2173687
Abstract: The influence of various growth parameters such as coverage, the AsH3 flow (V∕III ratio), and growth interrupts on the self-assembled growth of InAs∕GaAs quantum dots (QDs) by metal organic chemical vapor deposition is reported. Of the various growth parameters, the AsH3 flow has a particularly strong influence. Higher AsH3 flows during deposition led to a faster nucleation process and larger islands, while the presence of AsH3 after nucleation led to continued island ripening. We suggest that this is the result of increased indium redistribution from the highly strained wetting layer to the islands, and possibly between the islands, at higher AsH3 flows. A large defect density was observed by plan-view transmission electron microscopy, whenever the growth parameters led to larger islands. Using our optimized growth conditions we are able to avoid such defect generation and still achieve a high QD density (3×1010cm−2).
Publisher: American Association for the Advancement of Science (AAAS)
Date: 05-2020
Abstract: Terahertz (THz) radiation is an interesting region of the electromagnetic spectrum lying between microwaves and infrared. Non-ionizing and transparent to most fabrics, it is finding application in security screening and imaging but is also being developed for communication and chemical sensing. To date, most THz detectors have focused just on signal intensity, an effort that discards half the signal in terms of the full optical state, including polarization. Peng et al. developed a THz detector based on crossed nanowires (arranged in a hash structure) that is capable of resolving the full state of the THz light. The approach provides a nanophotonic platform for the further development of THz-based technologies. Science , this issue p. 510
Publisher: AIP Publishing
Date: 27-12-2003
DOI: 10.1063/1.1528304
Abstract: An experimental method of studying shifts between concentration-versus-depth profiles of vacancy- and interstitial-type defects in ion-implanted silicon is demonstrated. The concept is based on deep level transient spectroscopy measurements utilizing the filling pulse variation technique. The vacancy profile, represented by the vacancy–oxygen center, and the interstitial profile, represented by the interstitial carbon–substitutional carbon pair, are obtained at the same s le temperature by varying the duration of the filling pulse. The effect of the capture in the Debye tail has been extensively studied and taken into account. Thus, the two profiles can be recorded with a high relative depth resolution. Using low doses, point defects have been introduced in lightly doped float zone n-type silicon by implantation with 6.8 MeV boron ions and 680 keV and 1.3 MeV protons at room temperature. The effect of the angle of ion incidence has also been investigated. For all implantation conditions the peak of the interstitial profile is displaced towards larger depths compared to that of the vacancy profile. The litude of this displacement increases as the width of the initial point defect distribution increases. This behavior is explained by a simple model where the preferential forward momentum of recoiling silicon atoms and the highly efficient direct recombination of primary point defects are taken into account.
Publisher: IOP Publishing
Date: 14-01-2008
DOI: 10.1088/0957-4484/19/05/055205
Abstract: Strong suppression of the effects caused by the internal electric field in ZnO/ZnMgO quantum wells following ion-implantation and rapid thermal annealing, is revealed by photoluminescence, time-resolved photoluminescence, and band structure calculations. The implantation and annealing induces Zn/Mg intermixing, resulting in graded quantum well interfaces. This reduces the quantum-confined Stark shift and increases electron-hole wavefunction overlap, which significantly reduces the exciton lifetime and increases the oscillator strength.
Publisher: Elsevier BV
Date: 04-1997
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2008
Publisher: SPIE
Date: 07-2004
DOI: 10.1117/12.525966
Publisher: AIP Publishing
Date: 27-05-2013
DOI: 10.1063/1.4807506
Abstract: A bound-to-continuum quantum well solar cell structure is proposed, and the band structure and absorption spectra are analyzed by the use of an eight band k·p model. The structure is based on quantum wells that only support bound states for the valence band. The absence of bound conduction band states has a number of potential advantages, including a reduction of electron trapping and, therefore, a reduction of quantum well induced photocarrier recombination due to reduced spatial overlap of the electron and hole wavefunctions.
Publisher: AIP Publishing
Date: 24-09-2007
DOI: 10.1063/1.2790486
Abstract: Branched nanowire heterostructures of InAs∕GaAs were observed during Au-assisted growth of InAs on GaAs nanowires. The evolution of these branches has been determined through detailed electron microscopy characterization with the following sequence: (1) in the initial stage of InAs growth, the Au droplet is observed to slide down the side of the GaAs nanowire, (2) the downward movement of Au nanoparticle later terminates when the nanoparticle encounters InAs growing radially on the GaAs nanowire sidewalls, and (3) with further supply of In and As vapor reactants, the Au nanoparticles assist the formation of InAs branches with a well-defined orientation relationship with GaAs∕InAs core/shell stems. We anticipate that these observations advance the understanding of the kink formation in axial nanowire heterostructures.
Publisher: IEEE
Date: 2001
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C0JM00172D
Publisher: AIP Publishing
Date: 18-09-1995
DOI: 10.1063/1.115029
Abstract: Rutherford backscattering spectrometry-channeling, double-crystal x-ray diffraction, optical absorption studies, and electrical measurements have been carried out on 2 MeV Ga-implanted GaAs at fluences of 1×1015 and 5×1015 cm−2. Implanted s les exhibited a strain field associated with implantation-induced damage, low resistivity due to hopping conduction and mobilities of about 1 cm2/V s. Annealing of these s les at 600 °C caused substantial recovery of postimplant damage and an increase of resistivity of more than four orders of magnitude, with mobility up to about 2600 cm2/V s. Photocarrier lifetime of annealed s les is in the few picoseconds range. These properties are strikingly similar to those of arsenic implanted GaAs, suggesting that arsenic precipitates are unlikely to be solely responsible for short carrier lifetime in the latter case. Thus Ga-implanted GaAs may be an interesting prospect for fast optoelectronic device applications.
Publisher: Elsevier BV
Date: 03-2002
Publisher: Wiley
Date: 17-09-2015
Abstract: Controllable axial switching of polarity in GaAs nanowires with minimal tapering and perfect twin-free ZB structure based on the fundamental understanding of nanowire growth and kinking mechanism is presented. The polarity of the bottom segment is confirmed to be (111)A by atomically resolved scanning transmission electron microscopy.
Publisher: American Chemical Society (ACS)
Date: 25-01-2016
DOI: 10.1021/ACS.NANOLETT.5B04864
Abstract: We use temperature-dependent photoluminescence (PL), photoluminescence imaging, and time-resolved photoluminescence measurements to gain insights into the localization of excitons in single 2 nm GaAs/AlGaAs quantum well tube nanowires. PL spectra reveal the coexistence of localized and delocalized states at low temperatures, with narrow quantum dot-like emission lines on the high energy side of a broad emission band, and delocalized states on the low energy side. We find that the high energy QD-like emissions are metastable, disappearing at higher temperatures with only delocalized states (quantum well tube ground states) surviving. By comparing temperature- and time-dependent PL, we develop a theoretical model which provides insights into the confinement potentials and relaxation dynamics which localize the excitons in these quantum well tube nanowires.
Publisher: AIP Publishing
Date: 09-07-2012
DOI: 10.1063/1.4735002
Abstract: GaAs/AlxGa1−xAs core-shell nanowires were grown by metal organic chemical vapor deposition with optimized AlxGa1−xAs shell and twin-free Au-catalyzed GaAs cores. Time-resolved photoluminescence measurements were carried out on single nanowires at room temperature, revealing minority carrier lifetimes of 1.02 ± 0.43 ns, comparable to self-assisted nanowires grown by molecular beam epitaxy. The long minority carrier lifetimes are mainly attributed to improvement of the GaAs/AlxGa1−xAs interface quality. The upper limit of surface recombination velocity of the structure is calculated to be 1300 cm/s with the AlxGa1−xAs shell grown at 750 °C, which is comparable with planar double heterostructures.
Publisher: The Electrochemical Society
Date: 2006
DOI: 10.1149/1.2220066
Publisher: The Electrochemical Society
Date: 2005
DOI: 10.1149/1.1872016
Publisher: IOP Publishing
Date: 15-03-2006
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4NR06307D
Abstract: GaAs 1−x Sb x nanowires show zinc blende twin free structure at low TMSb flow while high TMSb flow results in inclined faults and nanowire kinking thanks to its surfactant role. Increase of wetting angle is observed, replying the change of surface energy.
Publisher: Wiley
Date: 22-03-2012
Abstract: The dynamics of free electron-hole pairs and excitons in GaAs-AlGaAs-GaAs core-shell-skin nanowires is investigated using femtosecond transient photoluminescence spectroscopy at 10 K. Following nonresonant excitation, a bimolecular interconversion of the initially generated electron-hole plasma into an exciton population is observed. This conducting-to-insulating transition appears to occur gradually over electron-hole charge pair densities of 2-4 × 10(16) cm(-3) . The smoothness of the Mott transition is attributed to the slow carrier-cooling during the bimolecular interconversion of free charge carriers into excitons and to the presence of chemical-potential fluctuations leading to inhomogeneous spectral characteristics. These results demonstrate that high-quality nanowires are model systems for investigating fundamental scientific effects in 1D heterostructures.
Publisher: American Chemical Society (ACS)
Date: 18-01-2013
DOI: 10.1021/NL304237B
Abstract: We report a novel phase separation phenomenon observed in the growth of ternary In(x)Ga(1-x)As nanowires by metalorganic chemical vapor deposition. A spontaneous formation of core-shell nanowires is investigated by cross-sectional transmission electron microscopy, revealing the compositional complexity within the ternary nanowires. It has been found that for In(x)Ga(1-x)As nanowires high precursor flow rates generate ternary In(x)Ga(1-x)As cores with In-rich shells, while low precursor flow rates produce binary GaAs cores with ternary In(x)Ga(1-x)As shells. First-principle calculations combined with thermodynamic considerations suggest that this phenomenon is due to competitive alloying of different group-III elements with Au catalysts, and variations in elemental concentrations of group-III materials in the catalyst under different precursor flow rates. This study shows that precursor flow rates are critical factors for manipulating Au catalysts to produce nanowires of desired composition.
Publisher: Institution of Engineering and Technology (IET)
Date: 1999
DOI: 10.1049/EL:19990554
Publisher: SPIE
Date: 24-09-2012
DOI: 10.1117/12.931309
Publisher: American Chemical Society (ACS)
Date: 16-11-2022
Abstract: Carrier-selective contacts have emerged as a promising architecture for solar cell fabrication. In this report, the first hole-selective III-V semiconductor solar cell is demonstrated using copper iodide (CuI) on i-GaAs. Surface passivation quality of GaAs is found to be essential for open-circuit voltage (
Publisher: American Chemical Society (ACS)
Date: 07-09-2011
DOI: 10.1021/NL2020262
Abstract: We report on the observation of nonlinear optical excitation and related photoluminescence from single InP semiconductor nanowires held in suspension using a gradient force optical tweezers. Photoexcitation of free carriers is achieved through absorption of infrared (1.17 eV) photons from the trapping source via a combination of two- and three-photon processes. This was confirmed by power-dependent photoluminescence measurements. Marked differences in spectral features are noted between nonlinear optical excitation and direct excitation and are related to band-filling effects. Direct observation of second harmonic generation in trapped InP nanowires confirms the presence of nonlinear optical processes.
Publisher: AIP Publishing
Date: 21-08-2006
DOI: 10.1063/1.2338552
Abstract: The influence of spherical nanoindentation on the band edge and deep level emission of single crystal c-axis ZnO has been studied by cathodoluminescence (CL) spectroscopy and monochromatic imaging. Excitonic emission is quenched at the indent site and defect emission in the range of 450–720nm is enhanced. Analysis of CL monochromatic images and spectra suggests that at least two different defect states are responsible for the broad defect emission band. Additionally, the indents result in a strong crystallographic dependence of the defect emission, producing a rosette feature with [112¯0] [21¯1¯0], and [12¯10] orientations that reflect the star-shaped luminescence quenching observed at the excitonic peak (390nm).
Publisher: AIP Publishing
Date: 22-04-1996
DOI: 10.1063/1.116147
Abstract: Proton irradiation and subsequent rapid-thermal annealing are used to create intermixing in GaAs-Al0.54Ga0.46As quantum wells of various thicknesses. Very large energy shifts (up to 200 meV) with no apparent saturation have been observed even up to a dose of about 4×1016 cm−2. This effect is explained in terms of the dilute irradiation damage and the evolution of discrete (point) defects during annealing. In comparison to heavy ion irradiation effects, high point defect fraction in the case of light ions leads to efficient intermixing with large energy shifts. Although much of the proton energy loss occurs across the quantum wells, the generated defect density is dilute, and hence good recovery in photoluminescence intensities is achieved after rapid thermal annealing.
Publisher: American Chemical Society (ACS)
Date: 16-01-2015
DOI: 10.1021/NL5038374
Abstract: We investigate the absorption properties of ensembles of wurtzite (WZ) InP nanowires (NWs) by high-resolution polarization-resolved photoluminescence excitation (PLE) spectroscopy at T = 10 K. The degree of linear polarization of absorbed light, ρ(abs), resulting from the PLE spectra is governed by a competition between the dielectric mismatch effect and the WZ selection rules acting differently on different optical transitions. These two contributions are deconvoluted with the help of finite-difference time-domain simulations, thus providing information about the symmetry of the three highest valence bands (A, B, and C) of WZ InP and the extent of the spin-orbit interaction on these states. Moreover, ρ(abs) shows two characteristic dips corresponding to the two sharp A and B exciton resonances in the PLE spectra. A model developed for the dip in A provides the first experimental evidence of an enhancement in the dielectric mismatch effect originating from the Coulomb interaction between electron and hole.
Publisher: IEEE
Date: 2006
Publisher: AIP Publishing
Date: 11-06-2007
DOI: 10.1063/1.2748845
Abstract: Impurity-free disordering (IFD) of the InAs quantum dots (QDs) capped with either an InP layer or an InGaAs∕InP bilayer is studied. The s les are coated with a SiO2 or TiO2 dielectric layer followed by rapid thermal annealing at 700, 750, 800, and 850°C for 30s. A large differential energy shift of 157meV is induced by SiO2 in the QDs capped with an InGaAs∕InP bilayer. Contrary to the reported results on the suppression of intermixing of GaAs based QDs by TiO2, the authors find that intermixing of InAs∕InP QDs is promoted by TiO2. X-ray photoelectron spectroscopy depth profiles show that both In and P outdiffuse to a TiO2 layer whereas Ga, In, and P outdiffuse to a SiO2 layer leading to different degrees of intermixing. The results indicate that a group V interstitial diffusion mechanism might be responsible for IFD of InAs∕InP QDs.
Publisher: American Chemical Society (ACS)
Date: 12-08-2013
DOI: 10.1021/NL402050Q
Abstract: We have investigated the dynamics of hot charge carriers in InP nanowire ensembles containing a range of densities of zinc-blende inclusions along the otherwise wurtzite nanowires. From time-dependent photoluminescence spectra, we extract the temperature of the charge carriers as a function of time after nonresonant excitation. We find that charge-carrier temperature initially decreases rapidly with time in accordance with efficient heat transfer to lattice vibrations. However, cooling rates are subsequently slowed and are significantly lower for nanowires containing a higher density of stacking faults. We conclude that the transfer of charges across the type II interface is followed by release of additional energy to the lattice, which raises the phonon bath temperature above equilibrium and impedes the carrier cooling occurring through interaction with such phonons. These results demonstrate that type II heterointerfaces in semiconductor nanowires can sustain a hot charge-carrier distribution over an extended time period. In photovoltaic applications, such heterointerfaces may hence both reduce recombination rates and limit energy losses by allowing hot-carrier harvesting.
Publisher: OSA
Date: 2016
Publisher: Elsevier BV
Date: 11-2013
Publisher: AIP Publishing
Date: 25-05-2015
DOI: 10.1063/1.4921788
Abstract: Thermally equilibrated nano-cavities are formed in ZnO by H implantation and subsequent high temperature annealing to determine the relative surface formation energies and step energies of ZnO from reverse Wulff construction and related analysis. H adsorption, vicinal surfaces, and surface polarity are found to play an important role in determining the final thermal equilibrium shape of the nano-cavities. Under H coverage, the O-terminated surface shows a significantly lower surface formation energy than the Zn-terminated surface.
Publisher: AIP Publishing
Date: 30-09-2003
DOI: 10.1063/1.1609634
Abstract: In this article the effect of rapid thermal annealing (RTA) on a 30 stacked InAs/GaAs, molecular beam epitaxially grown quantum dot infrared photodetector (QDIP) device is studied. Temperatures in the range of 600–800 °C for 60 s, typical of atomic interdiffusion methods are used. After rapid thermal annealing the devices exhibited large dark currents and no photoresponse could be measured. Double crystal x-ray diffraction and cross sectional transmission electron microscopy studies indicate that this could be the result of strain relaxation. V-shaped dislocations which extended across many quantum dot (QD) layers formed in the RTA s les. Smaller defect centers were observed throughout the as-grown s le and are also likely a strain relaxation mechanism. This supports the idea that strained structures containing dislocations are more likely to relax via the formation of dislocations and/or the propagation of existing dislocations, instead of creating atomic interdiffusion during RTA. Photoluminescence (PL) studies also found that Si related complexes developed in the Si doped GaAs contact layers with RTA. The PL from these Si related complexes overlaps and dominates the PL from our QD ground state.
Publisher: AIP Publishing
Date: 10-06-2002
DOI: 10.1063/1.1486264
Abstract: Contact-induced damage has been studied in single-crystal (wurtzite) ZnO by cross-sectional transmission electron microscopy (XTEM) and scanning cathodoluminescence (CL) monochromatic imaging. XTEM reveals that the prime deformation mechanism in ZnO is the nucleation of slip on both the basal and pyramidal planes. Some indication of dislocation pinning was observed on the basal slip planes. No evidence of either a phase transformation or cracking was observed by XTEM in s les loaded up to 50 mN with an ∼4.2 μm radius spherical indenter. CL imaging reveals a quenching of near-gap emission by deformation-produced defects. Both XTEM and CL show that this comparatively soft material exhibits extensive deformation damage and that defects can propagate well beyond the deformed volume under contact. Results of this study have significant implications for the extent of contact-induced damage during fabrication of ZnO-based (opto)electronic devices.
Publisher: AIP Publishing
Date: 08-03-2005
DOI: 10.1063/1.1875745
Abstract: Selective growth of InGaAs quantum dots on GaAs is reported. It is demonstrated that selective-area epitaxy can be used for in-plane bandgap energy control of quantum dots. Atomic force microscopy and cathodoluminescence are used for characterization of the selectively grown dots. Our results show that the composition, size, and uniformity of dots are determined by the dimensions of the mask used for patterning the substrate. Properties of dots can be selectively tuned by varying the mask dimensions. A single-step growth of a thin InGaAs quantum well and InGaAs quantum dots on the same wafer is demonstrated. By using a single-step growth, dots luminescing at different wavelengths, in the range 1150–1230nm, in different parts of the same wafer are achieved.
Publisher: IOP Publishing
Date: 09-10-2015
DOI: 10.1088/0957-4484/26/44/445202
Abstract: Antimonide-based ternary III-V nanowires (NWs) allow for a tunable bandgap over a wide range, which is highly interesting for optoelectronics applications, and in particular for infrared photodetection. Here we demonstrate room temperature operation of GaAs0.56Sb0.44 NW infrared photodetectors grown by metal organic vapor phase epitaxy. These GaAs0.56Sb0.44 NWs have uniform axial composition and show p-type conductivity with a peak field-effect mobility of ∼12 cm(2) V(-1) s(-1)). Under light illumination, single GaAs0.56Sb0.44 NW photodetectors exhibited typical photoconductor behavior with an increased photocurrent observed with the increase of temperature owing to thermal activation of carrier trap states. A broadband infrared photoresponse with a long wavelength cutoff at ∼1.66 μm was obtained at room temperature. At a low operating bias voltage of 0.15 V a responsivity of 2.37 (1.44) A/W with corresponding detectivity of 1.08 × 10(9) (6.55 × 10(8)) cm√Hz/W were achieved at the wavelength of 1.3 (1.55) μm, indicating that ternary GaAs0.56Sb0.44 NWs are promising photodetector candidates for small footprint integrated optical telecommunication systems.
Publisher: IOP Publishing
Date: 05-09-2006
Publisher: Wiley
Date: 31-01-2018
Publisher: Elsevier BV
Date: 11-1999
Publisher: SPIE
Date: 07-09-2018
DOI: 10.1117/12.2320720
Publisher: American Chemical Society (ACS)
Date: 15-08-2014
DOI: 10.1021/NL5021409
Abstract: We report the growth of stacking-fault-free and taper-free wurtzite InP nanowires with diameters ranging from 80 to 600 nm using selective-area metal-organic vapor-phase epitaxy and experimentally determine a quantum efficiency of ∼50%, which is on par with InP epilayers. We also demonstrate room-temperature, photonic mode lasing from these nanowires. Their excellent structural and optical quality opens up new possibilities for both fundamental quantum optics and optoelectronic devices.
Publisher: American Chemical Society (ACS)
Date: 05-04-2017
Publisher: Wiley
Date: 05-03-2007
Publisher: Elsevier BV
Date: 11-2018
Publisher: The Optical Society
Date: 14-12-2010
DOI: 10.1364/OL.35.004190
Publisher: IOP Publishing
Date: 31-08-2007
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2011
Publisher: IEEE
Date: 2005
Publisher: The Electrochemical Society
Date: 2000
DOI: 10.1149/1.1393464
Publisher: American Chemical Society (ACS)
Date: 27-06-2007
DOI: 10.1021/NL071162X
Publisher: Wiley
Date: 31-05-2016
Publisher: Springer Science and Business Media LLC
Date: 03-04-2017
DOI: 10.1557/ADV.2017.280
Publisher: American Physical Society (APS)
Date: 28-05-2002
Publisher: IEEE
Date: 2000
Publisher: IEEE
Date: 2000
Publisher: AIP Publishing
Date: 18-03-1996
DOI: 10.1063/1.116788
Publisher: IEEE
Date: 2000
Publisher: Elsevier BV
Date: 11-1999
Publisher: The Optical Society
Date: 03-04-2013
DOI: 10.1364/OE.21.008879
Publisher: AIP Publishing
Date: 23-10-2006
DOI: 10.1063/1.2364885
Abstract: Temperature-dependent polarized microphotoluminescence measurements of single GaAs∕AlGaAs core-shell nanowires are used to probe their electronic states. The low-temperature emission from these wires is strongly enhanced compared with that observed in bare GaAs nanowires and is strongly polarized, reflecting the dielectric mismatch between the nanowire and the surrounding air. The temperature-dependent band gap of the nanowires is seen to be somewhat different from that observed in bulk GaAs, and the PL rapidly quenches above 120K, with an activation energy of 17meV reflecting the presence of nonradiative defects.
Publisher: AIP Publishing
Date: 14-10-2013
DOI: 10.1063/1.4825153
Abstract: Phase stepping interferometry is used to measure the size of near-cylindrical nanowires. Nanowires with nominal radii of 25 nm and 50 nm were used to test this by comparing specific measured optical phase profile values with theoretical values calculated using a wave-optic model of the Phase stepping interferometry (PSI) system. Agreement within 10% was found, which enabled nanowire radii to be predicted within 4% of the nominal value. This demonstration highlights the potential capability for phase stepping interferometry to characterize single nanoparticles of known geometry in the optical far-field.
Publisher: American Chemical Society (ACS)
Date: 25-06-2018
Abstract: Photoelectrolysis of water using solar energy into storable and environment-friendly chemical fuel in the form of hydrogen provides a potential solution to address the environmental concerns and fulfill future energy requirements in a sustainable manner. Achieving efficient and spontaneous hydrogen evolution in water using solar light as the only energy input is a highly desirable but a difficult target. In this work, we report perovskite solar cell integrated CdS-based photoanode for unbiased photoelectrochemical hydrogen evolution. An integrated tandem device consisting of mesoporous CdS/TiO
Publisher: SPIE
Date: 18-09-2018
DOI: 10.1117/12.2320715
Publisher: AIP Publishing
Date: 15-03-2011
DOI: 10.1063/1.3552928
Abstract: Highly c-axis oriented ZnO thin films have been deposited on silicon substrates by planar rf magnetron sputtering under varying pressure (10–50 mTorr) and oxygen percentage (50–100%) in the reactive gas (Ar + O2) mixture. The as-grown films were found to be stressed over a wide range from −1 × 1011 to −2 × 108 dyne/cm2 that in turn depends strongly on the processing conditions, and the film becomes stress free at a unique combination of sputtering pressure and reactive gas composition. Raman spectroscopy and photoluminescence (PL) analyses identified the origin of stress as lattice distortion due to defects introduced in the ZnO thin film. FTIR study reveals that Zn-O bond becomes stronger with the increase in oxygen fraction in the reactive gas mixture. The lattice distortion or stress depends on the type of defects introduced during deposition. PL spectra show the formation of a shoulder in band emission with an increase in the processing pressure and are related to the presence of stress. The ratio of band emission to defect emission decreases with the increase in oxygen percentage from 50 to 100%. The studies show a correlation of stress with the structural, vibrational, and photoluminescence properties of the ZnO thin film. The systematic study of the stress will help in the fabrication of efficient devices based on ZnO film.
Publisher: American Chemical Society (ACS)
Date: 22-05-2017
DOI: 10.1021/ACS.NANOLETT.7B01488
Abstract: Nonlinear effects at the nanoscale are usually associated with the enhancement of electric fields in plasmonic structures. Recently emerged new platform for nanophotonics based on high-index dielectric nanoparticles utilizes optically induced magnetic response via multipolar Mie resonances and provides novel opportunities for nanoscale nonlinear optics. Here, we observe strong second-harmonic generation from AlGaAs nanoantennas driven by both electric and magnetic resonances. We distinguish experimentally the contribution of electric and magnetic nonlinear response by analyzing the structure of polarization states of vector beams in the second-harmonic radiation. We control continuously the transition between electric and magnetic nonlinearities by tuning polarization of the optical pump. Our results provide a direct observation of nonlinear optical magnetism through selective excitation of multipolar nonlinear modes in nanoantennas.
Publisher: AIP Publishing
Date: 06-01-2005
DOI: 10.1063/1.1844618
Abstract: Vacancy-type defect production in Al- and Si-implanted 4H–SiC has been studied as a function of ion fluence, ion flux, and implantation temperature in the projected ion range region by positron annihilation spectroscopy and Rutherford backscattering techniques. Ion channeling measurements show that the concentration of displaced silicon atoms increases rapidly with increasing ion fluence. In the ion fluence interval of 1013–1014cm−2 the positron annihilation parameters are roughly constant at a defect level tentatively associated with the acancy VCVSi. Above the ion fluence of 1014cm−2 larger vacancy clusters are formed. For implantations as a function of ion flux (cm−2s−1), ion channeling and positron annihilation measurements behave similarly, i.e., indicating increasing damage in the projected range region with increasing ion flux. However, for s les implanted at different temperatures the positron annihilation parameter S shows a clear minimum at approximately 100°C, whereas the normalized backscattering yield decrease continuously with increasing implantation temperature. This is explained by the formation of larger vacancy clusters when the implantation temperature is increased.
Publisher: Elsevier BV
Date: 04-2006
Publisher: IOP Publishing
Date: 24-10-2013
DOI: 10.1088/0957-4484/24/46/465602
Abstract: We demonstrate the growth of InP nanowires on Si(111) using a thin InP buffer layer. The buffer layer is grown using a two-step procedure. The initial layer formation is ensured by using a very low growth temperature. An extremely high V/III ratio is necessary to prevent In droplet formation at this low temperature. The second layer is grown on the initial layer at a higher temperature and we find that post-growth annealing of the buffer layer does not improve its crystal quality significantly. It is found that the layers inherently have the (111)B polarity. Nanowires grown on this buffer layer have the same morphology and optical properties as nanowires grown on InP (111)B substrates. The vertical yield of the nanowires grown on the buffer layer is over 97% and we also find that crystal defects in the buffer layer do not affect the morphology, vertical yield or optical properties of the nanowires significantly.
Publisher: Elsevier BV
Date: 07-2006
Publisher: AIP Publishing
Date: 12-07-2010
DOI: 10.1063/1.3463036
Abstract: We use time-resolved photoluminescence spectroscopy and photoluminescence excitation spectroscopy to measure the valence band parameters of hexagonal wurtzite InP nanowires. The A exciton emission and excitation energy is observed at 1.504 eV as expected. Excitation spectra show that the B and C hole bands are 30 and 161 meV above the A hole band. From these measurements, we obtain the crystal field and spin-orbit energies of 52 meV and 139 meV, respectively.
Publisher: IEEE
Date: 08-2015
Publisher: Wiley
Date: 12-01-2009
Publisher: IEEE
Date: 2000
Publisher: IOP Publishing
Date: 10-09-2014
Publisher: American Chemical Society (ACS)
Date: 11-12-2017
Abstract: We report on in idual-InAs nanowire optoelectronic devices which can be tailored to exhibit either negative or positive photoconductivity (NPC or PPC). The NPC photoresponse time and magnitude is found to be highly tunable by varying the nanowire diameter under controlled growth conditions. Using hysteresis characterization, we decouple the observed photoexcitation-induced hot electron trapping from conventional electric field-induced trapping to gain a fundamental insight into the interface trap states responsible for NPC. Furthermore, we demonstrate surface passivation without chemical etching which both enhances the field-effect mobility of the nanowires by approximately an order of magnitude and effectively eliminates the hot carrier trapping found to be responsible for NPC, thus restoring an "intrinsic" positive photoresponse. This opens pathways toward engineering semiconductor nanowires for novel optical-memory and photodetector applications.
Publisher: IOP Publishing
Date: 05-02-2013
Publisher: AIP Publishing
Date: 28-05-2007
DOI: 10.1063/1.2745264
Abstract: The authors investigate the effect of oxygen implantation and rapid thermal annealing in ZnO∕ZnMgO multiple quantum wells using photoluminescence. A blueshift in the photoluminescence is observed in the implanted s les. For a low implantation dose, a significant increase of activation energy and a slight increase of the photoluminescence efficiency are observed. This is attributed to the suppression of the point defect complexes and transformation between defect structures by implantation and subsequent rapid thermal annealing. A high dose of implantation leads to lattice damage and agglomeration of defects leading to large defect clusters, which result to an increase in nonradiative recombination.
Publisher: IEEE
Date: 09-2012
Publisher: Elsevier BV
Date: 03-2004
Publisher: The Optical Society
Date: 02-04-2013
DOI: 10.1364/OE.21.00A324
Publisher: AIP Publishing
Date: 30-10-2000
DOI: 10.1063/1.1320846
Abstract: Intersubband transitions in 1 MeV proton-irradiated GaAs/AlGaAs multiple quantum wells were studied using an optical absorption technique and isochronal thermal annealing. The intersubband transitions were completely depleted in s les irradiated with doses as low as 4×1014 cm−2. More than 80% recovery of these depleted transitions was achieved after the s les were thermally annealed at temperatures less than 650 °C. The total integrated areas and peak position energies of the intersubband transitions in irradiated and unirradiated s les were monitored as a function of annealing temperature. It was noted that the recovery of the depleted intersubband transitions in irradiated s les depend on the irradiation dose and thermal annealing temperature.
Publisher: AIP Publishing
Date: 28-05-2004
DOI: 10.1063/1.1760886
Abstract: Thermal-stress controlled interdiffusion in InGaAsN/GaAs quantum dots (QDs) has been studied by deposition of titanium oxide (TiO2) layers combined with rapid thermal annealing. Without TiO2 cap layers, blueshifting of the band gap from 1.033 to 1.180 eV at 77 K has been observed after annealing at 850 °C for 30 s due to the thermal interdiffusion. The thermal interdiffusion has been effectively suppressed by depositing TiO2 layers on the s les without degrading the photoluminescence properties. By a combination of annealing temperature and TiO2 thickness, controlled blueshifting of the band gap has been achieved. We suggest that the mechanism of suppression of thermal interdiffusion is the thermal stress imposed on the QD structure generated by TiO2 layers during annealing.
Publisher: Springer Science and Business Media LLC
Date: 31-08-2012
Abstract: InAs/GaAs(001) quantum dots grown by droplet epitaxy were investigated using electron microscopy. Misfit dislocations in relaxed InAs/GaAs(001) islands were found to be located approximately 2 nm above the crystalline s le surface, which provides an impression that the misfit dislocations did not form at the island/substrate interface. However, detailed microscopy data analysis indicates that the observation is in fact an artefact caused by the surface oxidation of the material that resulted in substrate surface moving down about 2 nm. As such, caution is needed in explaining the observed interfacial structure.
Publisher: Wiley
Date: 04-2006
DOI: 10.1111/J.1742-6723.2006.00823.X
Abstract: Paediatric emergency research is h ered by a number of barriers that can be overcome by a multicentre approach. In 2004, an Australia and New Zealand-based paediatric emergency research network was formed, the Paediatric Research in Emergency Departments International Collaborative (PREDICT). The founding sites include all major tertiary children's hospital EDs in Australia and New Zealand and a major mixed ED in Australia. PREDICT aims to provide leadership and infrastructure for multicentre research at the highest standard, facilitate collaboration between institutions, health-care providers and researchers and ultimately improve patient outcome. Initial network-wide projects have been determined. The present article describes the development of the network, its structure and future goals.
Publisher: IOP Publishing
Date: 25-04-2013
DOI: 10.1088/0957-4484/24/21/214006
Abstract: We have performed a comparative study of ultrafast charge carrier dynamics in a range of III-V nanowires using optical pump-terahertz probe spectroscopy. This versatile technique allows measurement of important parameters for device applications, including carrier lifetimes, surface recombination velocities, carrier mobilities and donor doping levels. GaAs, InAs and InP nanowires of varying diameters were measured. For all s les, the electronic response was dominated by a pronounced surface plasmon mode. Of the three nanowire materials, InAs nanowires exhibited the highest electron mobilities of 6000 cm² V⁻¹ s⁻¹, which highlights their potential for high mobility applications, such as field effect transistors. InP nanowires exhibited the longest carrier lifetimes and the lowest surface recombination velocity of 170 cm s⁻¹. This very low surface recombination velocity makes InP nanowires suitable for applications where carrier lifetime is crucial, such as in photovoltaics. In contrast, the carrier lifetimes in GaAs nanowires were extremely short, of the order of picoseconds, due to the high surface recombination velocity, which was measured as 5.4 × 10⁵ cm s⁻¹. These findings will assist in the choice of nanowires for different applications, and identify the challenges in producing nanowires suitable for future electronic and optoelectronic devices.
Publisher: AIP Publishing
Date: 14-04-2003
DOI: 10.1063/1.1569046
Abstract: In this work, titanium dioxide (TiO2) film was deposited onto the In0.5Ga0.5As/GaAs quantum-dot structure by electron-beam evaporation to investigate its effect on interdiffusion. A large redshifted and broadened spectrum from the dot emission was observed compared with that from the uncapped (but annealed) reference s le, indicating the suppression of thermal interdiffusion due to TiO2 deposition. The structure was also capped with a silicon dioxide (SiO2) single layer or SiO2/TiO2 bilayer with the thickness of SiO2 varied from ∼6 to ∼145 nm. In the former case, an increased amount of impurity-free vacancy disordering (IFVD) was introduced with the increase of SiO2 thickness due to the enhanced Ga outdiffusion into the film. With TiO2 deposited on top, IFVD and thermal interdiffusion were suppressed to different extents with the variation of SiO2 thickness. To explain the suppression of interdiffusion, thermal stress introduced by the large thermal expansion coefficient of TiO2 (when compared with GaAs) as well as the metallurgical reactions between the TiO2 and GaAs were proposed as possible mechanisms.
Publisher: SPIE
Date: 25-03-2005
DOI: 10.1117/12.592313
Publisher: IOP Publishing
Date: 09-05-2017
Publisher: American Chemical Society (ACS)
Date: 08-03-2012
DOI: 10.1021/CG201725G
Publisher: AIP Publishing
Date: 20-09-2010
DOI: 10.1063/1.3492836
Abstract: We report on a detailed analysis of the temperature dependent electrical properties of In0.5Ga0.5As/GaAs quantum dot solar cells. The effects leading to a reduction in the open circuit voltage are found to be the thermal injection of carriers from the n and p-type layers into the depletion region where they recombine with carriers occupying quantum dot states due to a thermal distribution. The departure of the device studied here from an ideal intermediate band solar cell is discussed.
Publisher: IOP Publishing
Date: 04-04-2018
Abstract: Radiation effects on semiconductor nanowires (NWs) have attracted the attention of the research community due to their potential applications in space and atomic fields. The effective implementation of NW devices in a radiation environment is a matter of concern. Here, the photoluminescence (PL) and time-resolved PL (TRPL) measurements were performed on both GaAs and InP NWs at room temperature before and after 1 MeV H
Publisher: AIP Publishing
Date: 05-03-2012
DOI: 10.1063/1.3691917
Abstract: Enhanced near infrared photoresponse in plasmonic InGaAs/GaAs quantum dot solar cells (QDSC) is demonstrated. Long wavelength light absorption in the wetting-layer and quantum-dot region of the quantum dot solar cell is enhanced through scattering of light by silver nanoparticles deposited on the solar cell surface. Plasmonic light trapping results in simultaneous increase in short-circuit current density by 5.3% and open circuit voltage by 0.9% in the QDSC, leading to an overall efficiency enhancement of 7.6%.
Publisher: Wiley
Date: 19-06-2017
Abstract: III–V ternary InGaAs nanowires have great potential for electronic and optoelectronic device applications however, the 3D structure and chemistry at the atomic‐scale inside the nanowires remain unclear, which hinders tailoring the nanowires for specific applications. Here, atom probe tomography is used in conjunction with a first‐principles simulation to investigate the 3D structure and chemistry of InGaAs nanowires, and reveals i) the nanowires form a spontaneous core–shell structure with a Ga‐enriched core and an In‐enriched shell, due to different growth mechanisms in the axial and lateral directions ii) the shape of the core evolves from hexagon into Reuleaux triangle and grows larger, which results from In outward and Ga inward interdiffusion occurring at the core–shell interface and iii) the irregular hexagonal shell manifests an anisotropic growth rate on {112}A and {112}B facets. Accordingly, a model in terms of the core–shell shape and chemistry evolution is proposed, which provides fresh insights into the growth of these nanowires.
Publisher: OSA
Date: 2017
Publisher: AIP Publishing
Date: 10-2001
DOI: 10.1063/1.1408273
Abstract: Wurtzite GaN epilayers are studied by cathodoluminescence (CL) spectroscopy. Results show that the intensities of donor–acceptor pair (DAP) and yellow luminescence (YL) peaks sublinearly depend on excitation density, presumably, due to saturation effects. The intensity of near-gap emission, however, exhibits a superlinear dependence on electron-beam excitation. In contrast to photoluminescence measurements, CL studies of GaN are usually performed in a regime with a strongly nonlinear dependence of luminescence intensities on excitation due to a large difference in carrier generation rates for these two techniques. As a result, the ratios of near-gap to YL and DAP emission intensities strongly depend on electron-beam current. Moreover, electron-beam spot size (i.e., beam focusing) dramatically affects CL intensity. An understanding of such saturation effects is necessary for a correct interpretation of CL spectra from GaN.
Publisher: American Chemical Society (ACS)
Date: 18-12-2015
DOI: 10.1021/NL5033843
Abstract: Spectroscopy and imaging in the terahertz (THz) region of the electromagnetic spectrum has proven to provide important insights in fields as erse as chemical analysis, materials characterization, security screening, and nondestructive testing. However, compact optoelectronics suited to the most powerful terahertz technique, time-domain spectroscopy, are lacking. Here, we implement single GaAs nanowires as microscopic coherent THz sensors and for the first time incorporated them into the pulsed time-domain technique. We also demonstrate the functionality of the single nanowire THz detector as a spectrometer by using it to measure the transmission spectrum of a 290 GHz low pass filter. Thus, nanowires are shown to be well suited for THz device applications and hold particular promise as near-field THz sensors.
Publisher: American Chemical Society (ACS)
Date: 15-09-2023
Publisher: American Chemical Society (ACS)
Date: 20-07-2022
Publisher: AIP Publishing
Date: 19-03-2012
DOI: 10.1063/1.3695165
Abstract: We study experimentally the nonlinear properties of fishnet metamaterials infiltrated with nematic liquid crystals and find that moderate laser powers result in significant changes of the optical transmission of the composite structures. We also show that the nonlinear response of our structure can be further tuned with a bias electric field, enabling the realization of electrically tunable nonlinear metamaterials.
Publisher: American Chemical Society (ACS)
Date: 18-12-2014
DOI: 10.1021/NL403299U
Abstract: We report an electron-beam based method for the nanoscale patterning of the poly(ethylene oxide)/LiClO4 polymer electrolyte. We use the patterned polymer electrolyte as a high capacitance gate dielectric in single nanowire transistors and obtain subthreshold swings comparable to conventional metal/oxide wrap-gated nanowire transistors. Patterning eliminates gate/contact overlap, which reduces parasitic effects and enables multiple, independently controllable gates. The method's simplicity broadens the scope for using polymer electrolyte gating in studies of nanowires and other nanoscale devices.
Publisher: SPIE
Date: 19-08-2010
DOI: 10.1117/12.860236
Publisher: Elsevier BV
Date: 06-2004
Publisher: IEEE
Date: 12-2006
Publisher: AIP Publishing
Date: 19-05-2015
DOI: 10.1063/1.4921109
Abstract: Exciton resonances are observed in photocurrent spectra of 80 nm wurtzite InP nanowire devices at low temperatures, which correspond to transitions between the A, B, and C valence bands and the lower conduction band. Photocurrent spectra for 30 nm WZ nanowires exhibit shifts of the exciton resonances to higher energy, which are consistent with finite element calculations of wavefunctions of the confined electrons and holes for the various bands.
Publisher: American Chemical Society (ACS)
Date: 03-10-2018
Abstract: III-V semiconductor multi-quantum-well nanowires (MQW NWs) via selective-area epitaxy (SAE) is of great importance for the development of nanoscale light-emitting devices for applications such as optical communication, silicon photonics, and quantum computing. To achieve highly efficient light-emitting devices, not only the high-quality materials but also a deep understanding of their growth mechanisms and material properties (structural, optical, and electrical) are extremely critical. In particular, the three-dimensional growth mechanism of MQWs embedded in a NW structure by SAE is expected to be different from that of those grown in a planar structure or with a catalyst and has not yet been thoroughly investigated. In this work, we reveal a distinctive radial growth evolution of InGaAs/InP MQW NWs grown by the SAE metal organic vapor-phase epitaxy (MOVPE) technique. We observe the formation of zinc blende (ZB) QW discs induced by the axial InGaAs QW growth on the wurtzite (WZ) base-InP NW and propose it as the key factor driving the overall structure of radial growth. The role of the ZB-to-WZ change in the driving of the overall growth evolution is supported by a growth formalism, taking into account the formation-energy difference between different facets. Despite a polytypic crystal structure with mixed ZB and WZ phases across the MQW region, the NWs exhibit high uniformity and desirable QW spatial layout with bright room-temperature photoluminescence at an optical communication wavelength of ∼1.3 μm, which is promising for the future development of high-efficiency light-emitting devices.
Publisher: Springer Science and Business Media LLC
Date: 24-10-2012
Abstract: In this letter, we quantitatively investigated epitaxial GaAs nanowires catalyzed by thin Au films of different thicknesses on GaAs (111) B substrates in a metal-organic chemical vapor deposition reactor. Prior to nanowire growth, the de-wetting of Au thin films to form Au nanoparticles on GaAs (111) B in AsH 3 ambient at different temperatures is investigated. It is found that with increasing film thickness, the size of the Au nanoparticles increases while the density of the nanoparticles reduces. Furthermore, higher annealing temperature produces larger Au nanoparticles for a fixed film thickness. As expected, the diameters and densities of the as-grown GaAs nanowires catalyzed by these thin Au films reflect these trends.
Publisher: Georg Thieme Verlag KG
Date: 2008
DOI: 10.1160/TH08-02-0078
Abstract: Elevated plasma fibronectin levels occur in various clinical states including arterial disease. Increasing evidence suggests that atherothrombosis and venous thromboembolism (VTE) share common risk factors. To assess the hypothesis that high plasma fibronectin levels are associated with VTE, we compared plasma fibronectin levels in the Scripps Venous Thrombosis Registry for 113VTE cases vs. age and sex matched controls. VTE cases had significantly higher mean fibronectin concentration compared to controls (127% vs. 103%, p .0001) the difference was greater for idiopathic VTE cases compared to secondary VTE cases (133% vs. 120%, respectively). Using a cut-off of % of the control values, the odds ratio (OR) for association of VTE for fibronectin plasma levels above the 90th percentile were 9.37 (95% CI 2.73–32.2 p .001) and this OR remained significant after adjustment for sex, age, body mass index (BMI), factor V Leiden and prothrombin nt20210A (OR 7.60,95% CI 2.14–27.0 p=0.002). In particular, the OR was statistically significant for idiopathic VTE before and after these statistical adjustments. For the total male cohort, the OR was significant before and after statistical adjustments and was not significant for the total female cohort. In summary, our results suggest that elevated plasma fibronectin levels are associated with VTE especially in males, and extend the potential association between biomarkers and risk factors for arterial atherothrombosis and VTE.
Publisher: AIP Publishing
Date: 12-2005
DOI: 10.1063/1.2140481
Abstract: Zinc oxide single crystals implanted at room temperature with high-dose (1.4×1017cm−2) 300 keV As+ ions are annealed at 1000–1200 °C. Damage recovery is studied by a combination of Rutherford backscattering/channeling spectrometry (RBS/C), cross-sectional transmission electron microscopy (XTEM), and atomic force microscopy. Results show that such a thermal treatment leads to the decomposition and evaporation of the heavily damaged layer instead of apparent defect recovery and recrystallization that could be inferred from RBS/C and XTEM data alone. This study shows that heavily damaged ZnO has relatively poor thermal stability compared to as-grown ZnO which is a significant result and has implications for understanding results on thermal annealing of ion-implanted ZnO.
Publisher: Springer Science and Business Media LLC
Date: 05-1997
Publisher: American Chemical Society (ACS)
Date: 04-09-2013
DOI: 10.1021/JP406294T
No related grants have been discovered for Chennupati Jagadish.