ORCID Profile
0000-0002-3811-9125
Current Organisation
University of Adelaide
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Quantum Optics | Nanophotonics | Nanotechnology | Nanofabrication, Growth and Self Assembly
Expanding Knowledge in the Physical Sciences | Emerging Defence Technologies |
Publisher: Elsevier BV
Date: 02-2020
Publisher: Hindawi Limited
Date: 2014
DOI: 10.1155/2014/278263
Publisher: AIP Publishing
Date: 09-02-2005
DOI: 10.1063/1.1852697
Abstract: The concept of below-threshold and above-threshold current injection efficiency of quantum well (QW) lasers is clarified. The analysis presented here is applied to the current injection efficiency of 1200nm emitting InGaAs and 1300nm emitting InGaAsN QW lasers. The role of heavy-hole leakage in the InGaAsN QW lasers is shown to be significant in determining the device temperature sensitivity. The current injection efficiency of QW lasers with large monomolecular recombination processes is shown to be less temperature sensitive. Excellent agreement between theory and experiment is obtained for both the 1200nm emitting InGaAs QW and the 1300nm emitting InGaAsN QW lasers. Suppression of thermionic carrier escape processes in the InGaAsN QW results in high performance 1300nm emitting lasers operating up to high temperature.
Publisher: AIP Publishing
Date: 05-2015
DOI: 10.1063/1.4921394
Abstract: The evaluation of Auger recombination process for dilute-As GaNAs alloy is presented. Our analysis indicates the suppression of interband Auger recombination mechanism in dilute-As GaNAs alloy in the green spectral regime. The interband Auger coefficient in dilute-As GaNAs alloy is shown as two orders of magnitude lower than that of its corresponding intraband Auger rate. Our results confirm that the second conduction band has a negligible effect on the interband Auger process in dilute-As GaNAs alloy due to the non-resonant condition of the process. Our findings show the importance of dilute-As GaNAs as an alternative visible material with low Auger recombination rates.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2005
Publisher: Institution of Engineering and Technology (IET)
Date: 2004
DOI: 10.1049/EL:20040474
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2002
Publisher: Wiley
Date: 12-2008
Publisher: IEEE
Date: 2011
Publisher: IEEE
Date: 10-2017
Publisher: AIP Publishing
Date: 23-09-2003
DOI: 10.1063/1.1613998
Abstract: Very low threshold-current-density InGaAsN quantum-well lasers with GaAsN barriers, grown using metalorganic chemical vapor deposition, have been realized with a room-temperature emission wavelength of 1317 nm. The GaAsN barriers are employed to extend the wavelength, to strain compensate the quantum well, and to improve the hole confinement inside the quantum well. RT threshold current densities of only 210–270 A/cm2 are measured for InGaAsN quantum-well lasers (Lcav=1000–2000 μm) with an emission wavelength of 1317 nm.
Publisher: IEEE
Date: 05-2008
Publisher: Optica Publishing Group
Date: 24-07-2009
DOI: 10.1364/OE.17.013747
Abstract: Improvement of light extraction efficiency of InGaN light emitting diodes (LEDs) using polydimethylsiloxane (PDMS) concave microstructures arrays was demonstrated. The size effect of the concave microstructures on the light extraction efficiency of III-Nitride LEDs was studied. Depending on the size of the concave microstructures, ray tracing simulations show that the use of PDMS concave microstructures arrays can lead to increase in light extraction efficiency of InGaN LEDs by 1.5 to 2.0 times. Experiments utilizing 2.0 micron thick PDMS with 1.0 micron diameter of the PDMS concave microstructures arrays demonstrated 1.70 times improvement in light extraction efficiency, which is consistent with improvement of 1.77 times predicted from simulation. The enhancement in light extraction efficiency is attributed to increase in effective photon escape cone due to PDMS concave microstructures arrays.
Publisher: IEEE
Date: 06-2009
Publisher: IEEE
Date: 10-2015
Publisher: OSA
Date: 2011
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2003
Publisher: Springer Science and Business Media LLC
Date: 14-04-2016
DOI: 10.1038/SREP24412
Abstract: A study on the electronic properties of the dilute-P GaN 1−x P x alloy using First-Principle Density Functional Theory (DFT) calculations is presented. Our results indicate a band gap energy coverage from 3.645 eV to 2.697 eV, with P-content varying from 0% to 12.5% respectively. In addition, through line fitting of calculated and experimental data, a bowing parameter of 9.5 ± 0.5 eV was obtained. The effective masses for electrons and holes are analyzed, as well as the split-off energy parameters where findings indicate minimal interband Auger recombination. The alloy also possesses the direct energy band gap property, indicating its strong potential as a candidate for future photonic device applications.
Publisher: SPIE-Intl Soc Optical Eng
Date: 12-10-2015
Publisher: SPIE
Date: 12-06-2002
DOI: 10.1117/12.470529
Publisher: IEEE
Date: 2006
Publisher: SPIE
Date: 10-02-2011
DOI: 10.1117/12.875901
Publisher: IEEE
Date: 12-2008
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2005
Publisher: SPIE
Date: 11-02-2010
DOI: 10.1117/12.843054
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2005
Publisher: Elsevier BV
Date: 04-2010
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2013
Publisher: Wiley
Date: 28-06-2023
Abstract: The study of optical resonators is of significant importance in terms of their ability to confine light in optical devices. A major drawback of optical resonators is the phenomenon of light emission due to their limited capacity for light confinement. Bound states in the continuum are gaining significant attention in the realization of optical devices due to their unique ability for reducing light scattering via interference mechanisms. This process can potentially suppress scattering, leading to improved optical performance. Using this concept, a metasurface having two elliptical silicon (Si) resonators nonidentically angled to create an out‐of‐plane asymmetry is studied. Various parameters are optimized by employing a genetic algorithm (GA) to subsequently achieve a high‐ Q factor at terahertz frequencies. Herein, the device is fabricated using a novel method, and a thick high‐index resonator is achieved. Terahertz measurements are carried out to validate the results. It is indicated in the experimental results that plasmons appear at the top surface of the metasurface and create strong sharp resonances that are sensitive to the external environment. Owing to strong field confinement ability, and high‐ Q factor, the metasurface is sensitive to its surrounding environment and can be essentially employed in terahertz sensing applications.
Publisher: AIP Publishing
Date: 28-03-2016
DOI: 10.1063/1.4944944
Abstract: In this work, the amorphous Eu3+-doped TiO2 spheres were synthesized by low cost mixed-solvent method, while the anatase and rutile spheres can be obtained by annealing the as-synthesized amorphous TiO2 spheres at elevated temperatures. The optical properties of Eu3+-doped TiO2 spheres were also investigated, and strong red emission (centered at 610 nm) with narrow line-width of 30 nm was observed under 465 nm or 394 nm excitations for the Eu3+-doped anatase TiO2 spheres. Our findings indicate the potential of using Eu3+-doped TiO2 spheres to achieve red emission with InGaN blue light emitting diodes (LEDs). Owing to the high light extraction efficiency in the GaN-based LEDs using anatase TiO2 spheres as demonstrated in our previous works, this work shows the strong potential of Eu3+-doped TiO2 spheres as the red phosphor material for high efficiency GaN-based white light-emitting diode.
Publisher: AIP Publishing
Date: 07-12-2020
DOI: 10.1063/5.0029488
Abstract: The natural band alignments of ScxAl1−xN/GaN heterojunctions, with Sc-contents ranging from 0% to 25%, are investigated by first-principles density functional theory with the local density approximation. Type-I ScxAl1−xN/GaN heterojunctions with large conduction band offsets (CBOs) and valence band offsets (VBOs) are found. The band alignment of nearly lattice-matched ScAlN (x = ∼18.75%) with respect to GaN (CBO = 1.74 eV, VBO = 0.34 eV) is also calculated for future implementation in GaN-based quantum wells and power devices. Our findings provide useful band parameters necessary for enabling the implementation of ScAlN alloys in GaN-based power and optoelectronic devices.
Publisher: IEEE
Date: 05-2008
Publisher: Springer Science and Business Media LLC
Date: 09-01-2008
Publisher: SPIE
Date: 12-02-2009
DOI: 10.1117/12.808600
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2012
Publisher: Springer Science and Business Media LLC
Date: 27-07-2017
DOI: 10.1038/S41598-017-06889-3
Abstract: The III-Nitride digital alloy (DA) is comprehensively studied as a short-period superlattice nanostructure consisting of ultra-thin III-Nitride epitaxial layers. By stacking the ultra-thin III-Nitride epitaxial layers periodically, these nanostructures are expected to have comparable optoelectronic properties as the conventional III-Nitride alloys. Here we carried out numerical studies on the InGaN DA showing the tunable optoelectronic properties of the III-Nitride DA. Our study shows that the energy gap of the InGaN DA can be tuned from ~0.63 eV up to ~2.4 eV, where the thicknesses and the thickness ratio of each GaN and InN ultra-thin binary layers within the DA structure are the key factors for tuning bandgap. Correspondingly, the absorption spectra of the InGaN DA yield broad wavelength tunability which is comparable to that of bulk InGaN ternary alloy. In addition, our investigation also reveals that the electron-hole wavefunction overlaps are remarkably large in the InGaN DA structure despite the existence of strain effect and build-in polarization field. Our findings point out the potential of III-Nitride DA as an artificially engineered nanostructure for optoelectronic device applications.
Publisher: IEEE
Date: 05-2007
Publisher: AIP Publishing
Date: 15-12-2005
DOI: 10.1063/1.2148620
Abstract: Pseudomorphic four-period GaAs0.978N0.022∕GaAs0.78Sb0.22 type-II multiquantum well structures were grown on (100) GaAs substrates by metalorganic vapor phase epitaxy at 530°C. The GaAs0.978N0.022 layers were grown at a V/III ratio of 685 and N∕V ratio of 0.96, whereas the GaAs0.78Sb0.22 was grown at a V/III ratio of 3.8 and Sb∕V ratio of 0.8. The superlattice peaks in the x-ray diffraction θ-2θ scans around the (400) GaAs peak were fitted using a dynamical simulation model to determine layer thickness and alloy compositions. The GaAsN and GaAsSb thicknesses were ∼8nm and ∼5nm, respectively. The photoluminescence (PL) spectra were obtained at 30K and the PL peak energy was found to match the type-II transition energy obtained from a 10-band k∙p model. Postgrowth annealing under arsine-H2 with a N2 cooldown was found to increase the low temperature PL intensity and result in the appearance of luminescence at room temperature.
Publisher: AIP Publishing
Date: 08-2018
DOI: 10.1063/1.5036978
Abstract: The electronic properties of dilute-P AlN1-xPx alloys are investigated by means of First-Principle Density Functional Theory (DFT) calculations, where the phosphorus (P) content is varied from 0% up to 6.25%. Band structure calculations indicate significant modifications of the electronic properties with the introduction of P-atoms, with the possibility of tuning the energy band gap from 6.19eV down to 4.32eV by inserting 6.25% P-content in the AlN-based system. The carrier effective masses and lattice parameters (a and c) were analyzed, and a large bowing parameter of b = 28.3 ± 0.5 eV was found. Moreover, our findings suggest a potential pathway to engineer the valence band crossover between the crystal-field split-off (CH) band and the heavy hole (HH) band by inserting low amounts of P-content (∼1-2%) into the AlN1-xPx alloy. Thus, the dilute-P AlN1-xPx alloys may serve as potential candidates for implementation as the active region material for dominant transverse electric (TE) polarization for deep-UV emitting devices.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2013
Publisher: IEEE
Date: 10-2007
Publisher: AIP Publishing
Date: 02-06-2003
DOI: 10.1063/1.1581978
Abstract: Extremely low threshold-current-density In0.4Ga0.6As quantum-well (QW) lasers have been realized in the 1215–1233 nm wavelength regime. The measured room-temperature threshold current density of the InGaAs QW lasers with a cavity length of 1000 μm is only 90 A/cm2 at an emission wavelength of 1233 nm.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2006
Publisher: AIP Publishing
Date: 13-09-2010
DOI: 10.1063/1.3488825
Abstract: The optical gain characteristics of high Al-content AlGaN quantum wells (QWs) are analyzed for deep UV lasers. The effect of crystal-field split-off hole (CH) and heavy-hole (HH) bands crossover on the gain characteristics of AlGaN QW with AlN barriers is analyzed. Attributing to the strong transition between conduction–CH bands, the TM spontaneous emission recombination rate is enhanced significantly for high Al-content AlGaN QWs. Large TM-polarized material gain is shown as achievable for high Al-content AlGaN QWs, which indicates the feasibility of TM lasing for lasers emitting at ∼220–230 nm.
Publisher: IEEE
Date: 09-2018
Publisher: American Chemical Society (ACS)
Date: 05-06-2008
DOI: 10.1021/LA801100G
Abstract: Convective deposition of a monolayer of microspheres by drawing a meniscus of a suspension across a substrate is used to fabricate microlens arrays to enhance the photon extraction efficiency of light emitting diodes (LEDs). The self-assembly of a colloidal crystal within the blade-drawn thin film is dominated by capillary forces and the thickness of this crystal depends on many parameters, including the deposition rate and particle size. This study investigates these and other parameters such as angle and hydrophobicity of the deposition blade that have not previously been considered. Using a confocal laser scanning microscope, the local and long-range order of the deposited particles are evaluated by the radial distribution function, and the fraction of the number of nearest neighbors and local bond order, demonstrating the dependence of the microstructure on the deposition parameters. Our results suggest previous descriptions of the critical deposition parameters are inadequate for understanding how various processing conditions influence deposition. For instance, increasing the deposition blade angle from 20 degrees up to 90 degrees requires an increase in deposition rate to achieve a monolayer deposition. The microlens arrays were fabricated on LEDs where polystyrene and silica are coated in consecutive depositions. Heat is used to sacrifice the polystyrene layers to result in an ordered array of partially buried silica microspheres that act as lenses to scatter light from the device. Enhancement in light extraction efficiency of 2.66 times was demonstrated for InGaN-based light emitting diodes employing micron scale microlens arrays with 1 um diameter silica microspheres.
Publisher: Springer Science and Business Media LLC
Date: 24-02-2016
DOI: 10.1038/SREP22215
Abstract: The band structures of dilute-As AlNAs alloys with As composition ranging from 0% up to 12.5% are studied by using First-Principle Density Functional Theory (DFT) calculation. The energy band gap shows remarkable reduction from 6.19 eV to 3.87 eV with small amount of As content in the AlNAs alloy, which covers the deep ultraviolet (UV) spectral regime. A giant bowing parameter of 30.5 eV ± 0.5 eV for AlNAs alloy is obtained. In addition, our analysis shows that the crossover between crystal field split-off (CH) band and heavy hole (HH) bands occurs in the dilute-As AlNAs alloy with As-content of ~1.5%. This result implies the possibility of dominant transverse electric (TE)-polarized emission by using AlNAs alloy with dilute amount of As-content. Our findings indicate the potential of dilute-As AlNAs alloy as the new active region material for TE-polarized III-Nitride-based deep UV light emitters.
Publisher: Elsevier BV
Date: 11-2008
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2009
Publisher: SPIE
Date: 10-02-2011
DOI: 10.1117/12.875125
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2002
DOI: 10.1109/68.992572
Publisher: AIP Publishing
Date: 2015
DOI: 10.1063/1.4906569
Abstract: Density functional theory (DFT) calculations with the local density approximation (LDA) functional are employed to investigate the band alignment of dilute-As GaNAs alloys with respect to the GaN alloy. Conduction and valence band positions of dilute-As GaNAs alloy with respect to the GaN alloy on an absolute energy scale are determined from the combination of bulk and surface DFT calculations. The resulting GaN / GaNAs conduction to valence band offset ratio is found as approximately 5:95. Our theoretical finding is in good agreement with experimental observation, indicating the upward movements of valence band at low-As content dilute-As GaNAs are mainly responsible for the drastic reduction of the GaN energy band gap. In addition, type-I band alignment of GaN / GaNAs is suggested as a reasonable approach for future device implementation with dilute-As GaNAs quantum well, and possible type-II quantum well active region can be formed by using InGaN / dilute-As GaNAs heterostructure.
Publisher: Elsevier BV
Date: 10-2020
Publisher: OSA
Date: 2012
Publisher: OSA
Date: 2010
Publisher: AIP Publishing
Date: 30-09-2002
DOI: 10.1063/1.1511290
Publisher: SPIE
Date: 07-07-2003
DOI: 10.1117/12.475793
Publisher: AIP Publishing
Date: 29-04-2003
DOI: 10.1063/1.1572470
Abstract: The metalorganic chemical vapor deposition of a highly strained InGaAsN quantum-well (QW) surrounded by (In)GaAsP direct barrier layers is investigated. We found that growth pause annealing with AsH3, performed immediately before and after the growth of the QW, significantly improves the optical quality of InGaAsN QW with (In)GaAsP direct barriers. The utilization of larger band gap barrier materials, such as InGaAsP or GaAsP, will potentially lead to reduced carrier leakage from the QW laser structures.
Publisher: OSA
Date: 2010
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2003
Publisher: SPIE
Date: 11-02-2010
DOI: 10.1117/12.842742
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2013
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2013
Publisher: SPIE
Date: 07-02-2008
DOI: 10.1117/12.763973
Publisher: AIP Publishing
Date: 12-07-2010
DOI: 10.1063/1.3462324
Abstract: We have investigated the photoluminescence spectra from GaN/AlN asymmetric-coupled quantum wells grown by metal-organic chemical vapor deposition. Deep ultraviolet photoluminescence peaks with photon energies up to 5.061 eV and dramatically improved intensities at low temperatures are identified due to recombination of electrons in the AlN coupling barrier with heavy holes in the GaN quantum wells. Photoluminescence quenching caused by relocation of photogenerated electrons under large internal electric fields, inherent in GaN/AlN asymmetric-coupled quantum wells, is observed.
Publisher: SPIE
Date: 11-02-2010
DOI: 10.1117/12.842509
Publisher: SPIE
Date: 10-02-2011
DOI: 10.1117/12.875002
Publisher: IOP Publishing
Date: 08-12-2010
Publisher: SPIE
Date: 11-02-2010
DOI: 10.1117/12.842869
Publisher: SPIE
Date: 2012
DOI: 10.1117/12.909633
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2009
Publisher: Springer Science and Business Media LLC
Date: 26-10-2017
DOI: 10.1038/S41598-017-14234-X
Abstract: We explore how crystallographic order and orientation affect the tribological (friction and wear) performance of gallium nitride (GaN), through experiments and theory. Friction and wear were measured in every direction on the c-plane of GaN through rotary wear experiment. This revealed a strong crystallographic orientation dependence of the sliding properties of GaN a 60° periodicity of wear rate and friction coefficient was observed. The origin of this periodicity is rooted in the symmetry presented in wurtzite hexagonal lattice structure of III-nitrides. The lowest wear rate was found as 0.6 × 10 −7 mm 3 /Nm with $$\\bar{1}$$ 1 ¯ 00 , while the wear rate associated with $$\\bar{2}$$ 2 ¯ 10 had the highest wear rate of 1.4 × 10 −7 mm 3 /Nm. On the contrary, higher friction coefficient can be observed along $$\\bar{1}$$ 1 ¯ 00 while lower friction coefficient always appeared along $$\\bar{2}$$ 2 ¯ 10 . We developed a simple molecular statics approach to understand energy barriers associated with sliding and material removal this calculated change of free energy associated with sliding revealed that there were smaller energy barriers sliding along $$\\bar{2}$$ 2 ¯ 10 as compared to the $$\\bar{1}$$ 1 ¯ 00 direction.
Publisher: Wiley
Date: 07-2008
Publisher: IOP Publishing
Date: 09-2020
Publisher: IEEE
Date: 10-2007
Publisher: AIP Publishing
Date: 02-01-2008
DOI: 10.1063/1.2829600
Abstract: We present a visible III-nitride gain medium based on type-II InGaN-GaNAs quantum well (QW), employing thin dilute-As (∼3%) GaNAs layer. The utilization of GaNAs layer shifts the hole confinement to the center of the type-II QW, which significantly reduces the charge separation effect. The optical gain and spontaneous recombination rate of the type-II InGaN-GaNAs QW are analyzed and compared with those of conventional InGaN QW emitting in the blue regime (λ∼450nm), using six-band k.p formalism for energy dispersion of the III-nitride wurtzite semiconductor. The use of type-II QW leads to significant improvement in the optical gain and spontaneous recombination rate.
Publisher: SPIE
Date: 08-02-2007
DOI: 10.1117/12.700767
Publisher: IEEE
Date: 09-2019
Publisher: Elsevier BV
Date: 03-2020
Publisher: AIP Publishing
Date: 10-2017
DOI: 10.1063/1.5000519
Abstract: Data are presented on strain compensation in InGaN-based multiple quantum wells (MQW) using AlGaN interlayers (ILs). The MQWs consist of five periods of InxGa1-xN/AlyGa1-yN/GaN emitting in the green (λ ∼ 535 nm ± 15 nm), and the AlyGa1-yN IL has an Al composition of y = 0.42. The IL is varied from 0 - 2.1 nm, and the relaxation of the MQW with respect to the GaN template layer varies with IL thickness as determined by reciprocal space mapping about the (202¯5) reflection. The minimum in the relaxation occurs at an interlayer thickness of 1 nm, and the MQW is nearly pseudomorphic to GaN. Both thinner and thicker ILs display increased relaxation. Photoluminescence data shows enhanced spectral intensity and narrower full width at half maximum for the MQW with 1 nm thick ILs, which is a product of pseudomorphic layers with lower defect density and non-radiative recombination.
Publisher: Springer Science and Business Media LLC
Date: 15-05-2015
DOI: 10.1038/SREP10219
Abstract: A computational model was developed to analyze electrical conductivity of random metal nanowire networks. It was demonstrated for the first time through use of this model that a performance gain in random metal nanowire networks can be achieved by slightly restricting nanowire orientation. It was furthermore shown that heavily ordered configurations do not outperform configurations with some degree of randomness randomness in the case of metal nanowire orientations acts to increase conductivity.
Publisher: IEEE
Date: 09-2018
Publisher: AIP Publishing
Date: 04-03-2003
DOI: 10.1063/1.1558218
Abstract: We calculate the thermionic escape times of electrons and holes in InGaAsN and InGaAs quantum wells using the most recent input data. The short thermionic escape time of holes from the InGaAsN quantum well indicates that hole leakage may be a significant factor in the poorer temperature characteristics of InGaAsN quantum-well lasers compared to those of InGaAs devices. We suggest a structure that results in an increased escape time, which will allow the reduction of hole leakage in these devices.
Publisher: Springer Science and Business Media LLC
Date: 13-01-2016
DOI: 10.1038/SREP19271
Abstract: The design of InGaN/dilute-As GaNAs interface quantum well (QW) leads to significant redshift in the transition wavelength with improvement in electron-hole wave function overlap and spontaneous emission rate as compared to that of the conventional In 0.2 Ga 0.8 N QW. By using self-consistent six-band k·p band formalism, the nitride active region consisting of 30 Å In 0.2 Ga 0.8 N and 10 Å GaN 0.95 As 0.05 interface QW leads to 623.52 nm emission wavelength in the red spectral regime. The utilization of 30 Å In 0.2 Ga 0.8 N/10 Å GaN 0.95 As 0.05 interface QW also leads to 8.5 times enhancement of spontaneous emission rate attributed by the improvement in electron-hole wavefunction overlap, as compared to that of conventional 30 Å In 0.35 Ga 0.65 N QW for red spectral regime. In addition, the transition wavelength of the interface QW is relatively unaffected by the thickness of the dilute-As GaNAs interface layer (beyond 10 Å). The analysis indicates the potential of using interface QW concept in nitride-based light-emitting diodes for long wavelength emission.
Publisher: Springer Science and Business Media LLC
Date: 12-2017
DOI: 10.1038/S41598-017-17033-6
Abstract: The internal quantum efficiency (IQE) of an electrically-driven GaN:Eu based device for red light emission is analyzed in the framework of a current injection efficiency model (CIE). The excitation path of the Eu +3 ion is decomposed in a multiple level system, which includes the carrier transport phenomena across the GaN/GaN:Eu/GaN active region of the device, and the interactions among traps, Eu +3 ions and the GaN host. The identification and analysis of the limiting factors of the IQE are accomplished through the CIE model. The CIE model provides a guidance for high IQE in the electrically-driven GaN:Eu based red light emitters.
Publisher: AIP Publishing
Date: 03-10-2019
DOI: 10.1063/1.5120302
Abstract: We propose a type-II AlInN/ZnGeN2 quantum well (QW) structure serving as the active region for ultraviolet (UV) laser diodes. A remarkably low threshold current density can be achieved using the type-II AlInN/ZnGeN2 QW structure, providing a pathway for the realization of electrically-driven nitride-based semiconductor UV laser diodes. ZnGeN2 has both a very similar lattice constant and bandgap to GaN. Its large band offsets with GaN enable the potential of serving as a hole confinement layer to increase the electron-hole wavefunction overlap in the active region. In this study, we investigate the spontaneous emission and gain properties of type-II AlInN/ZnGeN2 QWs with different ZnGeN2 layer thicknesses. Our findings show that the use of ZnGeN2 layers in the active region provides a significant improvement in hole carrier confinement, which results in ∼5 times enhancement of the electron-hole wave function overlap. Such an enhancement provides the ability to achieve a significant increase (∼6 times) in the spontaneous emission rate and material gain, along with a remarkable reduction in threshold carrier density compared to the conventional AlGaN-based QW design, which is essential for practical UV laser diodes.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2002
Publisher: American Chemical Society (ACS)
Date: 29-06-2018
Abstract: We show that sliding on the surface of GaN can permanently change the surface band structure, resulting in an increased degree of band bending by more than 0.5 eV. We hypothesize that shear and contact stresses introduce vacancies that cause a spatially variant band bending. Band bending is observed by shifts and broadening of core-level binding energies toward lower values in X-ray photoelectron spectroscopy. The extent of band bending is controlled by humidity, number of sliding cycles and applied load, presenting opportunities for scalable tuning of the degree of band bending on a GaN surface. Scanning transmission electron microscopy revealed that the epitaxy of GaN was preserved up to the surface with regions of defects near the surface. The hypothesized mechanism of band bending is shear-induced defect generation, which has been shown to affect the surface states. The ability to introduce band bending at the GaN surface is promising for applications in photovoltaics, photocatalysis, gas sensing, and photoelectrochemical processes.
Publisher: AIP Publishing
Date: 27-09-2010
DOI: 10.1063/1.3493188
Abstract: The design of InGaN-delta-InN quantum wells (QWs) leads to significant redshift for nitride active region with large electron-hole wave function overlap (Γe_hh) and spontaneous emission rate. The analysis was carried out by using self-consistent six-band k⋅p band formalism. The design of active region consisting of 30 Å In0.25Ga0.75N QW with InN delta-layer leads to large Γe_hh of & % with emission wavelength in the yellow and red spectral regimes, which is applicable for nitride-based light-emitting diodes.
Publisher: Springer Science and Business Media LLC
Date: 15-02-2018
DOI: 10.1038/S41598-018-21434-6
Abstract: A novel III-Nitride digital alloy (DA) with ultra-broadband optical gain is proposed. Numerical analysis shows a 50-period InN/GaN DA yields minibands that are densely quantized by numerous confined states. Interband transitions between the conduction and valence minibands create ultra-broadband optical gain spectra with bandwidths up to ~1 μm that can be tuned from the red to infrared. In addition, the ultra-broadband optical gain, bandwidth, and spectral coverage of the III-Nitride DA is very sensitive to layer thickness and other structural design parameters. This study shows the promising potential of the III-Nitride DAs with tunable ultra-broadband interband optical gain for use in semiconductor optical lifiers and future III-Nitride photonic integration applications.
Publisher: IOP Publishing
Date: 20-03-2008
Publisher: Springer Science and Business Media LLC
Date: 26-03-2019
DOI: 10.1038/S41598-019-41286-Y
Abstract: The band structure of the dilute-As GaNAs material is explained by the hybridization of localized As-impurity states with the valance band structure of GaN. Our approach employs the use of Density Functional Theory (DFT) calculated band structures, along with experimental results, to determine the localized As-impurity energy level and coupling parameters in the band anti-crossing (BAC) k ∙ p model for N-rich alloys. This model captures the reduction of bandgap with increasing arsenic incorporation and provides a tool for device-level design with the material within the context of the k ∙ p formalism. The analysis extends to calculating the effect of the arsenic impurities on hole (heavy, light and split-off) effective masses and predicting the trend of the bandgap across the entire composition range.
Publisher: MDPI AG
Date: 04-03-2020
DOI: 10.3390/S20051401
Abstract: Exceptional advancement has been made in the development of graphene optical nanoantennas. They are incorporated with optoelectronic devices for plasmonics application and have been an active research area across the globe. The interest in graphene plasmonic devices is driven by the different applications they have empowered, such as ultrafast nanodevices, photodetection, energy harvesting, biosensing, biomedical imaging and high-speed terahertz communications. In this article, the aim is to provide a detailed review of the essential explanation behind graphene nanoantennas experimental proofs for the developments of graphene-based plasmonics antennas, achieving enhanced light–matter interaction by exploiting graphene material conductivity and optical properties. First, the fundamental graphene nanoantennas and their tunable resonant behavior over THz frequencies are summarized. Furthermore, incorporating graphene–metal hybrid antennas with optoelectronic devices can prompt the acknowledgment of multi-platforms for photonics. More interestingly, various technical methods are critically studied for frequency tuning and active modulation of optical characteristics, through in situ modulations by applying an external electric field. Second, the various methods for radiation beam scanning and beam reconfigurability are discussed through reflectarray and leaky-wave graphene antennas. In particular, numerous graphene antenna photodetectors and graphene rectennas for energy harvesting are studied by giving a critical evaluation of antenna performances, enhanced photodetection, energy conversion efficiency and the significant problems that remain to be addressed. Finally, the potential developments in the synthesis of graphene material and technological methods involved in the fabrication of graphene–metal nanoantennas are discussed.
Publisher: Elsevier BV
Date: 02-2012
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 02-2021
Publisher: IEEE
Date: 05-2020
Publisher: IEEE
Date: 09-2012
Publisher: IEEE
Date: 09-2012
Publisher: AIP Publishing
Date: 10-08-2009
DOI: 10.1063/1.3204446
Abstract: Three-layer staggered InGaN quantum wells (QWs) light-emitting diodes (LEDs) emitting at 520–525 nm were grown by metal-organic chemical vapor deposition by employing graded growth-temperature profile. The use of staggered InGaN QW, with improved electron-hole wave functions overlap design, leads to an enhancement of its radiative recombination rate. Both cathodoluminescence and electroluminescence measurements of three-layer staggered InGaN QW LED exhibited enhancements by 1.8–2.8 and 2.0–3.5 times, respectively, over those of conventional InGaN QW LED.
Publisher: AIP Publishing
Date: 06-01-2020
DOI: 10.1063/1.5119371
Abstract: The dilute-As InyGa1 − yN1 − xAsx alloys are explored by performing first-principles density functional theory (DFT) calculations, where the In-content is varied from 0% up to 18.75% and the As-content is varied from 0% up to 3.13%. The obtained band structures indicate a direct bandgap semiconductor, whose electronic properties are modified significantly by the addition of As-atoms into the InGaN-based system. The lattice parameters (a and c) are analyzed, and the bowing parameters of the dilute-As InGaNAs are analyzed and discussed. The electronic properties indicate the dilute-As InyGa1 − yN1 − xAsx alloys as a potential new material alternative for achieving longer wavelength emission, while utilizing a low In-content (& %).
Publisher: IEEE
Date: 09-2018
Publisher: SPIE
Date: 07-02-2008
DOI: 10.1117/12.763362
Publisher: IEEE
Date: 2006
Publisher: IEEE
Date: 11-2008
Publisher: The Optical Society
Date: 28-07-2017
DOI: 10.1364/BOE.8.003856
Publisher: IEEE
Date: 2006
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2008
Publisher: OSA
Date: 2012
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2013
Publisher: Elsevier BV
Date: 06-2020
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2010
Publisher: AIP Publishing
Date: 15-08-2011
DOI: 10.1063/1.3624761
Abstract: The Seebeck coeeficients of AlInN alloys, grown by metalorganic vapor phase epitaxy, with In-contents (x) from 0.38% up to 21.34%, were characterized and analyzed from room temperature (T = 300 K) up to high temperature (T = 382 K). The Seebeck coefficients of the n-type AlInN alloys show significant enhancement at higher temperature up to 382 K, in comparison to those measured at room temperature. Large Seebeck coefficients (602.0– 1233.2 μV/K) were obtained for the lattice-matched Al0.83In0.17N alloy (n = 5.1 × 1018 cm−3) from T = 300 K up to T = 382 K. The improvement of Seebeck coefficients for the n-type AlInN alloys will lead to ∼1.5–4 times improvement of the thermopower at higher temperatures.
Publisher: SPIE
Date: 07-02-2008
DOI: 10.1117/12.763804
Publisher: SPIE
Date: 09-02-2006
DOI: 10.1117/12.646174
Publisher: The Optical Society
Date: 08-07-2015
DOI: 10.1364/AO.54.006305
Publisher: IEEE
Date: 09-2012
Publisher: AIP Publishing
Date: 03-2011
DOI: 10.1063/1.3553880
Abstract: Thermoelectric properties of AlInN alloys, grown by metalorganic vapor phase epitaxy (MOVPE), with In-contents (x) from 11% up to 21.34% were characterized and analyzed at room temperature. The thermoelectric figure of merit (Z*T) values of the n-Al1−xInxN alloys were measured as high as 0.391 up to 0.532 at T = 300 K. The use of high In-content (x = 21.34%) AlInN alloys leads to significant reduction in thermal conductivity [κ = 1.62 W/(mK)] due to the increased alloy scattering, however, the optimized thermoelectric material was obtained for AlInN alloy with In-content of 17% attributed to its large power factor.
Publisher: AIP Publishing
Date: 09-2011
DOI: 10.1063/1.3631823
Abstract: Plane view and cross-section transmission electron microscopy (TEM) images were used to compare the density, character, and curvature of dislocations developed during metalorganic vapor phase epitaxy (MOVPE) of GaN on planar c-plane sapphire with those developed during growth on nano-patterned c-plane sapphire. Scanning electron microscopy (SEM) characterization of GaN films at different stages of growth for both types of substrates complemented the TEM investigation. GaN growth on wafers patterned with an array of submicron sapphire bumps exhibited relatively uniform nucleation and initial growth, as well as early island coalescence. It is suggested that this coalescence results in a relatively small fraction of dislocations with partial screw character at the surface of the films grown on the patterned substrate, and that this may be responsible for the improvements in carrier lifetime and device efficiency seen in earlier studies on similar sapphire substrates.
Publisher: IEEE
Date: 10-2017
Publisher: AIP Publishing
Date: 11-02-2005
DOI: 10.1063/1.1868070
Abstract: We compare the gain and radiative efficiency characteristics of an InGaAsN and an InGaAs laser structure where the devices are identical except for the nitrogen content and emission wavelength. We find that the inclusion of nitrogen has little impact on the gain spectra except for the required shift to longer wavelength and that the intrinsic gain-radiative current characteristics may be slightly better for the nitrogen-containing materials. The radiative efficency is reduced by a factor of 4 in the s les containing nitrogen due to increased nonradiative recombination.
Publisher: IEEE
Date: 10-2007
Publisher: IEEE
Date: 12-2008
Publisher: AIP Publishing
Date: 15-08-2008
DOI: 10.1063/1.2970107
Abstract: Type-II InGaN–GaNAs quantum wells (QWs) with thin dilute-As (∼3%) GaNAs layer are analyzed self-consistently as improved III-nitride gain media for diode lasers. The band structure is calculated by using a six-band k⋅p formalism, taking into account valence band mixing, strain effect, spontaneous and piezoelectric polarizations, as well as the carrier screening effect. The type-II InGaN–GaNAs QW structure allows large electron-hole wave function overlap by confining the hole wave function in the GaNAs layer of the QW. The findings based on self-consistent analysis indicate that type-II InGaN-GaNAs QW active region results in superior performance for laser diodes, in comparison to that of conventional InGaN QW. Both the spontaneous emission radiative recombination rate and optical gain of type-II InGaN–GaNAs QW structure are significantly enhanced. Reduction in the threshold current density of InGaN–GaNAs QW lasers is also predicted.
Publisher: AIP Publishing
Date: 30-01-2006
DOI: 10.1063/1.2171486
Abstract: Low temperature (30K) long wavelength photoluminescence emission (λ=1400–1600nm) from metalorganic chemical vapor deposition grown InGaAsN–GaAsSb type II “W” quantum wells (QWs), on GaAs substrates has been demonstrated. Thin layers (2–3nm) and high antimony-content (30%) GaAsSb were utilized in this study for realizing satisfactory wave function overlap and long wavelength emission. Tensile strained GaAsP barriers effectively improve the material structural and luminescence properties of the compressive strained active region. Room temperature photoluminescence data show that the type-II QW design is a promising candidate for realizing long wavelength GaAs-based diode lasers beyond 1500nm.
Publisher: AIP Publishing
Date: 06-2010
DOI: 10.1063/1.3407564
Abstract: Staggered InGaN quantum wells (QWs) are analyzed as improved gain media for laser diodes (LDs) lasing at 440 and 500 nm. The calculation of band structure is based on a 6-band k⋅p method taking into account the valence band mixing, strain effect, and spontaneous and piezoelectric polarizations as well as the carrier screening effect. Staggered InGaN QWs with two-layer and three-layer step-function like In-content InGaN QWs structures are investigated to enhance the optical gain as well as to reduce the threshold current density for LDs emitting at 440 and 500 nm. Our analysis shows that the optical gain is enhanced by 1.5–2.1 times by utilizing the staggered InGaN QW active region emitting at 440 nm, which leads to a reduction of the threshold current density up to 24% as compared to that of the conventional InGaN QW laser. Staggered InGaN QWs with enhanced optical gain shows significantly reduced blue-shift as carrier density increases, which enables nitride QWs with high optical gain in the green spectral regime. The use of green-emitting three-layer staggered InGaN QW is also expected to lead to reduction in the threshold carrier density by 30%.
Publisher: AIP Publishing
Date: 26-11-2007
DOI: 10.1063/1.2816891
Abstract: Improvement of light extraction efficiency of InGaN quantum wells light emitting diodes (LEDs) using SiO2 olystyrene microspheres was demonstrated experimentally. The utilization of SiO2 olystyrene microlens arrays on InGaN quantum wells LEDs, deposited via rapid convective deposition, allows the increase of the effective photon escape cone and reduction in the Fresnel reflection. Improvement of output power by 219% for InGaN quantum wells LEDs emitting at peak wavelength of 480nm with SiO2 olystyrene microspheres microlens arrays was demonstrated.
Publisher: SPIE
Date: 12-02-2009
DOI: 10.1117/12.809079
Publisher: OSA
Date: 2013
Publisher: IEEE
Date: 09-2018
Publisher: AIP Publishing
Date: 17-09-2018
DOI: 10.1063/1.5046857
Abstract: Room temperature luminescence of epitaxial InGaN quantum dots (QDs) formed by quantum sized-controlled photoelectrochemical (QSC-PEC) etching and passivation layer regrowth is demonstrated. QSC-PEC etching is performed on a 7.5 nm thick In0.20Ga0.80N layer emitting at ∼514–521 nm and with a laser diode emitting at 445 nm. Parameters such as etch bias (0.9 V and 1.5 V), laser average power (20 mW/cm2 and 100 mW/cm2), and laser operating conditions (pulsed and continuous wave) are explored. QSC-PEC etching of In0.20Ga0.80N requires a minimum bias (& .9 V) and pulsed laser conditions in order to form QDs. After etching, the QDs do not exhibit photoluminescence due to defect recombination. Regrowth of passivation layers consisting of a 2 nm thick Al0.45Ga0.55N layer and a 11 nm thick GaN layer reduce the defect recombination, and room temperature photoluminescence is observed at room temperature at ∼435–445 nm with narrow full-width at half-maximum of ∼35 nm.
Publisher: SPIE
Date: 12-02-2009
DOI: 10.1117/12.808542
Publisher: IEEE
Date: 05-2007
Publisher: IEEE
Date: 10-2015
Publisher: The Optical Society
Date: 22-07-2015
DOI: 10.1364/PRJ.3.000184
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2011
Publisher: AIP Publishing
Date: 30-06-2003
DOI: 10.1063/1.1591238
Abstract: Comtinuous-wave (cw) operation of organometallic vapor phase epitaxy-grown In0.4Ga0.6As0.995N0.005 quantum well (QW) lasers has been realized, at a room-temperature near-threshold emission wavelength of 1.295 μm, with a threshold-current density of 220 A/cm2 for 2000 μm cavity-length (Lcav) devices. A threshold current density of only 615 A/cm2 was achieved for cw operation at a temperature of 100 °C, with an emission wavelength of 1.331 μm. A maximum cw-output power of 1.8 W was obtained for InGaAsN QW lasers with cavity lengths of 1000 and 2000 μm, at a heat-sink temperature of 20 °C.
Publisher: AIP Publishing
Date: 04-2019
DOI: 10.1063/1.5086979
Abstract: A reduction of the threshold current density of InGaN quantum well (QW) lasers is found from the usage of AlGaInN barriers. Large bandgap and strain-managing AlGaInN barriers surrounding the InGaN quantum wells’ (QWs) active regions are investigated via the 6-band self-consistent k·p formalism for their spontaneous emission, material gain, and threshold current density properties. In this study, quaternary AlGaInN alloys both lattice-matched and tensile-strained to GaN, with bandgaps ranging from 3.4 eV to 5.2 eV, are employed as thin barriers (∼1 nm) surrounding the InGaN active region. The AlGaInN barriers provide strong carrier confinement, which improves the electron and hole wavefunction overlap by ∼25%, while simultaneously reducing the strain relaxation in the active region. This study shows that InGaN QWs surrounded by AlGaInN barriers improve the material gain by ∼30%, reduce the threshold carrier density by ∼18%, and reduce the threshold current density by ∼40% over the conventional InGaN/GaN QW structure. Our results indicate that the AlGaInN barriers substantially enhance the radiative efficiency and reduce the power consumption for light emitting diodes (LEDs) and laser diodes (LDs), making them very attractive candidates for the design of low threshold optoelectronic devices.
Publisher: Wiley
Date: 12-08-2019
Publisher: IEEE
Date: 09-2020
Publisher: SPIE
Date: 06-06-2001
DOI: 10.1117/12.429800
Publisher: SPIE
Date: 11-02-2010
DOI: 10.1117/12.842931
Publisher: AIP Publishing
Date: 03-12-2019
DOI: 10.1063/1.5126965
Abstract: The recombination rates in InGaN/AlGaN/GaN multiple quantum wells (MQWs) emitting in the green-yellow and grown with different Al compositions in the AlGaN interlayer (IL) are shown. By transforming measurements on radiative efficiency, absorption, and differential carrier lifetime, the radiative and nonradiative rates are determined. The IL Al composition controls lattice relaxation of the MQWs, as determined by X-ray reciprocal space mapping, and, therefore, defect formation. For the most pseudomorphic MQWs, the Shockley-Read-Hall (SRH) A coefficient is minimized and is similar to reports at shorter (blue and green) wavelengths. It is an order of magnitude smaller than a conventional InGaN/GaN MQW and is the most significant factor behind the improvement in radiative efficiency using the IL. The radiative B coefficient is also reduced and a minimum for the most pseudomorphic MQWs due to a reduction in the electron-hole wavefunction overlap. However, the decrease in A is more significant and leads to an overall improvement in the radiative efficiency. These recombination rate measurements confirm that if the SRH recombination is controlled, then the severe reduction of radiative recombination with an increased emitting wavelength is one of the main challenges in realizing high efficiency, long-wavelength InGaN-based MQW emitters operating at low to moderate current densities.
Publisher: SPIE
Date: 12-02-2009
DOI: 10.1117/12.808695
Publisher: AIP Publishing
Date: 17-01-2013
DOI: 10.1063/1.4775605
Abstract: Photoluminescence (PL) spectra of InGaN/GaN multiple quantum wells excited by ultrafast laser pulses are investigated over broad ranges of excitation levels and temperatures. The PL peak energy undergoes blue, red, zero, and blue shifts with increasing the excitation fluence density. Such a peculiar behavior can be explained based on competing processes of screening of the built-in electric field by the photogenerated carriers, band-gap renormalization, and band-filling effect. We have also measured and analyzed the dependence of the PL energy and linewidth on the temperature. Due to the interplay between the band-gap renormalization and band-filling effect, the PL energy shifts to the highest value, whereas the PL linewidth reaches the minimum value at ≈60 K.
Publisher: MDPI AG
Date: 04-06-2020
DOI: 10.3390/S20113187
Abstract: Plasmonic antennas are attractive optical components of the optoelectronic devices, operating in the far-infrared regime for sensing and imaging applications. However, low optical absorption hinders its potential applications, and their performance is limited due to fixed resonance frequency. In this article, a novel gate tunable graphene-metal hybrid plasmonic antenna with stacking configuration is proposed and investigated to achieve tunable performance over a broad range of frequencies with enhanced absorption characteristics. The hybrid graphene-metal antenna geometry is built up with a hexagon radiator that is supported by the Al2O3 insulator layer and graphene reflector. This stacked structure is deposited in the high resistive Si wafer substrate, and the hexagon radiator itself is a sandwich structure, which is composed of gold hexagon structure and two multilayer graphene stacks. The proposed antenna characteristics i.e., tunability of frequency, the efficiency corresponding to characteristics modes, and the tuning of absorption spectra, are evaluated by full-wave numerical simulations. Besides, the unity absorption peak that was realized through the proposed geometry is sensitive to the incident angle of TM-polarized incidence waves, which can flexibly shift the maxima of the absorption peak from 30 THz to 34 THz. Finally, an equivalent resonant circuit model for the investigated antenna based on the simulations results is designed to validate the antenna performance. Parametric analysis of the proposed antenna is carried out through altering the geometric parameters and graphene parameters in the Computer Simulation Technology (CST) studio. This clearly shows that the proposed antenna has a resonance frequency at 33 THz when the graphene sheet Fermi energy is increased to 0.3 eV by applying electrostatic gate voltage. The good agreement of the simulation and equivalent circuit model results makes the graphene-metal antenna suitable for the realization of far-infrared sensing and imaging device containing graphene antenna with enhanced performance.
Publisher: IEEE
Date: 05-2008
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2009
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2013
Publisher: SPIE
Date: 04-2005
DOI: 10.1117/12.597115
Publisher: IOP Publishing
Date: 08-2005
DOI: 10.1143/JJAP.44.6204
Abstract: The effects of nitrogen incorporation into the In 0.4 Ga 0.6 As 1- x N x /GaAs single quantum wells (SQWs), where x = 0.5 and 2%, grown on GaAs substrates by metalorganic chemical vapor deposition (MOCVD) were investigated using photoluminescence (PL) and high-resolution transmission electron microscopy (HRTEM). The evolution of the excitation-dependent PL and PL-peak position with temperature between 10 and 300 K shows that quantum-dot-like states occurred at that high nitrogen incorporation ( x = 2%) and were confirmed by an HRTEM image which showed small dark regions about 2–3 nm in size was found in the interface of In 0.4 Ga 0.6 As 0.98 N 0.02 and GaAs. Our investigations indicate that high nitrogen incorporation into the In 0.4 Ga 0.6 As 1- x N x /GaAs system influenced carrier localization and might cause the formation of the dot-like states.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2013
Publisher: AIP Publishing
Date: 12-2011
DOI: 10.1063/1.3668117
Abstract: The spontaneous emission characteristics of green- and red-emitting InGaN quantum wells (QWs) on ternary InGaN substrate are analyzed, and the radiative recombination rates for the QWs grown on ternary substrate were compared with those of InGaN QWs on GaN templates. For green- and red-emitting InGaN QWs on In0.15Ga0.85N substrate, the spontaneous emission rates were found as ∼2.5-3.2 times of the conventional approach. The enhancement in spontaneous emission rate can be achieved by employing higher In-content InGaN ternary substrate, which is also accompanied by a reduction in emission wavelength blue-shift from the carrier screening effect. The use of InGaN substrate is expected to result in the ability for growing InGaN QWs with enhanced spontaneous emission rates, as well as reduced compressive strain, applicable for green- and red-emitting light-emitting diodes.
Publisher: IEEE
Date: 05-2008
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2013
Publisher: SPIE
Date: 12-02-2009
DOI: 10.1117/12.808561
Publisher: AIP Publishing
Date: 17-11-2008
DOI: 10.1063/1.3030883
Abstract: Phonon-assisted anti-Stokes photoluminescence (ASPL) in the ultraviolet region has been observed in the GaN film grown on a Si (111) substrate. The ASPL peaks are observable only at sufficiently low temperatures. In addition, even if the photon energy is ≈318meV below the transition energy for bound excitons, the ASPL peaks can be still observed. Based on our analysis, the donor-acceptor pairs and bound excitons have played primary roles in the generation of ASPL. Upon the absorption of photons, the ionizations of the neutral donors and neutral acceptors are assisted by longitudinal-optical phonons.
Publisher: SPIE
Date: 10-02-2011
DOI: 10.1117/12.875980
Publisher: Springer Science and Business Media LLC
Date: 10-03-2016
DOI: 10.1038/SREP22983
Abstract: The optical gain and spontaneous emission characteristics of low In-content AlInN-delta-GaN quantum wells (QWs) are analyzed for deep ultraviolet (UV) light emitting diodes (LEDs) and lasers. Our analysis shows a large increase in the dominant transverse electric (TE) polarized spontaneous emission rate and optical gain. The remarkable enhancements in TE-polarized optical gain and spontaneous emission characteristics are attributed to the dominant conduction (C)-heavy hole (HH) transitions achieved by the AlInN-delta-GaN QW structure, which could lead to its potential application as the active region material for high performance deep UV emitters. In addition, our findings show that further optimizations of the delta-GaN layer in the active region are required to realize the high performance AlInN-based LEDs and lasers with the desired emission wavelength. This work illuminates the high potential of the low In-content AlInN-delta-GaN QW structure to achieve large dominant TE-polarized spontaneous emission rates and optical gains for high performance AlN-based UV devices.
Publisher: AIP Publishing
Date: 04-10-2004
DOI: 10.1063/1.1794898
Abstract: We propose and simulate dilute-nitride midwave-infrared (3–6μm) laser structures, whose type-II “W” active regions (InAsN∕GaAsSb∕InAsN∕GaInP) are designed for growth on InP substrates. Besides taking advantage of the relative maturity of InP-based processing technology, this approach allows the substrate to serve as the bottom optical cladding layer, and for a top InP clad to provide high thermal conductivity for epitaxial-side-down mounting. Band structure and optical analyses project that the proposed lasers should produce nearly as much gain as current type-II W devices on GaSb substrates.
Publisher: SPIE
Date: 10-02-2011
DOI: 10.1117/12.875995
Publisher: Springer Science and Business Media LLC
Date: 19-01-2015
Publisher: SPIE
Date: 04-2005
DOI: 10.1117/12.597123
Publisher: OSA
Date: 2010
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2009
Publisher: Elsevier BV
Date: 2021
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2001
DOI: 10.1109/68.914313
Publisher: Springer Science and Business Media LLC
Date: 07-11-2017
DOI: 10.1038/S41598-017-15302-Y
Abstract: A physically intuitive current injection efficiency model for a GaN:Eu quantum well (QW) has been developed to clarify the necessary means to achieve device quantum efficiency higher than the state-of-the-art GaN:Eu system for red light emission. The identification and analysis of limiting factors for high internal quantum efficiencies (IQE) are accomplished through the current injection efficiency model. In addition, the issue of the significantly lower IQE in the electrically-driven GaN:Eu devices in comparison to the optically-pumped GaN:Eu devices is clarified in the framework of this injection efficiency model. The improved understanding of the quantum efficiency issue through current injection efficiency model provides a pathway to address the limiting factors in electrically-driven devices. Based on our developed injection efficiency model, several experimental approaches have been suggested to address the limitations in achieving high IQE GaN:Eu QW based devices in red spectral regime.
Publisher: The Optical Society
Date: 23-07-2013
DOI: 10.1364/OME.3.001149
Publisher: AIP Publishing
Date: 09-09-2003
DOI: 10.1063/1.1611279
Abstract: Carrier leakage processes are shown experimentally as one of the factors contributing to the temperature sensitivity of InGaAsN quantum well lasers. The utilization of the direct barriers of GaAs0.85P0.15 instead of GaAs, surrounding the InGaAsN quantum-well (QW)-active region, leads to significant suppression of carrier leakage at elevated temperatures of 90–100 °C. Threshold current densities of only 390 and 440 A/cm2 was achieved for InGaAsN QW lasers (Lcav=2000 μm) with GaAs0.85P0.15-direct barriers at temperature of 80 and 90 °C, respectively.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2011
Publisher: IEEE
Date: 09-2020
Publisher: IEEE
Date: 05-2008
Publisher: Institution of Engineering and Technology (IET)
Date: 12-2009
Publisher: Elsevier BV
Date: 04-2008
Publisher: Springer Science and Business Media LLC
Date: 06-09-2018
DOI: 10.1038/S41598-018-31821-8
Abstract: Metal-nitrides of hafnium nitride (HfN), zirconium nitride (ZrN) and titanium nitride (TiN) are investigated as plasmonic materials to enhance the internal quantum efficiency of a GaN:Eu red light emitter. Theoretical calculations are performed to evaluate the surface plasmon polariton dispersion relation and Purcell enhancement factor for a single metal-nitride layer on top of the GaN:Eu emitter. Our findings suggest that among the metal-nitrides investigated in this study, TiN is the most promising candidate for use as plasmonic material to increase the internal quantum efficiency in GaN:Eu red light emitters.
Publisher: SPIE
Date: 28-04-2005
DOI: 10.1117/12.591023
Publisher: Wiley
Date: 23-05-2016
Publisher: SPIE
Date: 10-02-2011
DOI: 10.1117/12.875079
Publisher: IEEE
Date: 10-2015
Publisher: IEEE
Date: 09-2018
Publisher: IEEE
Date: 09-2018
Publisher: Elsevier BV
Date: 04-2020
Publisher: OSA
Date: 2011
Publisher: SPIE
Date: 08-02-2007
DOI: 10.1117/12.700775
Publisher: SPIE
Date: 28-08-2008
DOI: 10.1117/12.802482
Publisher: IEEE
Date: 09-2020
Publisher: IEEE
Date: 09-2007
Publisher: IEEE
Date: 10-2011
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2013
Publisher: MDPI AG
Date: 20-03-2014
Publisher: IEEE
Date: 10-2017
Publisher: Elsevier BV
Date: 2006
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2012
Publisher: IEEE
Date: 05-2007
Publisher: AIP Publishing
Date: 11-04-2011
DOI: 10.1063/1.3580628
Abstract: Double-metallic Au/Ag layers deposited on top of InGaN/GaN quantum wells (QWs) are used to tune the Purcell peak enhancement of the radiative recombination rate for nitride light-emitting diodes. By modifying the Au/Ag thicknesses, the Purcell factor can be widely tuned between the surface plasmon frequencies of Au/GaN and Ag/GaN. Photoluminescence studies demonstrated the concept of the Purcell factor tuning by using the double-metallic Au/Ag layers.
Publisher: Elsevier BV
Date: 02-2018
Publisher: Elsevier BV
Date: 12-2004
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2008
Publisher: OSA
Date: 2011
Publisher: Springer Science and Business Media LLC
Date: 11-12-2017
DOI: 10.1038/S41598-017-17504-W
Abstract: We present a Density Functional Theory (DFT) analysis of the optical properties of dilute-As GaN 1−x As x alloys with arsenic (As) content ranging from 0% up to 12.5%. The real and imaginary parts of the dielectric function are investigated, and the results are compared to experimental and theoretical values for GaN. The analysis extends to present the complex refractive index and the normal-incidence reflectivity. The refractive index difference between GaN and GaNAs alloys can be engineered to be up to ~0.35 in the visible regime by inserting relatively low amounts of As-content into the GaN system. Thus, the analysis elucidates on the birefringence of the dilute-As GaNAs alloys and comparison to other experimentally characterized III-nitride systems is drawn. Our findings indicate the potential of GaNAs alloys for III-nitride based waveguide and photonic circuit design applications.
Publisher: Springer Science and Business Media LLC
Date: 19-09-2017
DOI: 10.1038/S41598-017-12125-9
Abstract: The AlN/GaN digital alloy (DA) is a superlattice-like nanostructure formed by stacking ultra-thin ( ≤ 4 monolayers) AlN barriers and GaN wells periodically. Here we performed a comprehensive study on the electronics and optoelectronics properties of the AlN/GaN DA for mid- and deep-ultraviolet (UV) applications. Our numerical analysis indicates significant miniband engineering in the AlN/GaN DA by tuning the thicknesses of AlN barriers and GaN wells, so that the effective energy gap can be engineered from ~3.97 eV to ~5.24 eV. The band structure calculation also shows that the valence subbands of the AlN/GaN DA is properly rearranged leading to the heavy-hole (HH) miniband being the top valence subband, which results in the desired transverse-electric polarized emission. Furthermore, our study reveals that the electron-hole wavefunction overlaps in the AlN/GaN DA structure can be remarkably enhanced up to 97% showing the great potential of improving the internal quantum efficiency for mid- and deep-UV device application. In addition, the optical absorption properties of the AlN/GaN DA are analyzed with wide spectral coverage and spectral tunability in mid- and deep-UV regime. Our findings suggest the potential of implementing the AlN/GaN DA as a promising active region design for high efficiency mid- and deep-UV device applications.
Publisher: AIP Publishing
Date: 14-05-2018
DOI: 10.1063/1.5028257
Abstract: Significant enhancement in green emission by integrating a thin AlInN barrier layer, or interlayer (IL), in an InGaN/GaN multiple quantum well (MQW) is demonstrated. The MQWs investigated here contains 5 periods of an InGaN QW, a 1 nm thick AlInN IL, and a 10 nm thick GaN barrier grown by metalorganic chemical vapor deposition. To accommodate the optimum low-pressure (20 Torr) growth of the AlInN layer a growth flow sequence with changing pressure is devised. The AlInN IL MQWs are compared to InGaN/AlGaN/GaN MQWs (AlGaN IL MQWs) and conventional InGaN/GaN MQWs. The AlInN IL MQWs provide benefits that are similar to AlGaN ILs, by aiding in the formation of abrupt heterointerfaces as indicated by X-ray diffraction omega-2theta (ω-2θ) scans, and also efficiency improvements due to high temperature annealing schedules during barrier growth. Room temperature photoluminescence of the MQW with AlInN ILs shows similar performance to MQWs with AlGaN ILs, and ∼4–7 times larger radiative efficiency (pump intensity dependent) at green wavelengths than conventional InGaN/GaN MQWs. This study shows the InGaN-based MQWs with AlInN ILs are capable of achieving superior performance to conventional InGaN MQWs emitting at green wavelengths.
Publisher: AIP Publishing
Date: 27-08-2007
DOI: 10.1063/1.2775334
Abstract: Staggered InGaN quantum wells (QWs) grown by metal-organic chemical vapor deposition are demonstrated as improved active region for visible light emitters. Theoretical studies indicate that InGaN QW with step-function-like In content in the quantum well offers significantly improved radiative recombination rate and optical gain in comparison to the conventional type-I InGaN QW. Experimental results of light emitting diode (LED) structure utilizing staggered InGaN QW show good agreement with theory. Polarization band engineering via staggered InGaN quantum well allows enhancement of radiative recombination rate, leading to the improvement of photoluminescence intensity and LED output power.
Publisher: OSA
Date: 2011
Publisher: IEEE
Date: 09-2019
Publisher: Wiley
Date: 06-2012
Publisher: SPIE
Date: 09-02-2006
DOI: 10.1117/12.646114
Publisher: Springer Science and Business Media LLC
Date: 02-02-2018
DOI: 10.1038/S41598-018-19513-9
Abstract: A correction to this article has been published and is linked from the HTML version of this paper. The error has been fixed in the paper.
Publisher: Springer Science and Business Media LLC
Date: 15-04-2011
Abstract: Highly uniform InGaN-based quantum dots (QDs) grown on a nanopatterned dielectric layer defined by self-assembled diblock copolymer were performed by metal-organic chemical vapor deposition. The cylindrical-shaped nanopatterns were created on SiN x layers deposited on a GaN template, which provided the nanopatterning for the epitaxy of ultra-high density QD with uniform size and distribution. Scanning electron microscopy and atomic force microscopy measurements were conducted to investigate the QDs morphology. The InGaN/GaN QDs with density up to 8 × 10 10 cm -2 are realized, which represents ultra-high dot density for highly uniform and well-controlled, nitride-based QDs, with QD diameter of approximately 22-25 nm. The photoluminescence (PL) studies indicated the importance of NH 3 annealing and GaN spacer layer growth for improving the PL intensity of the SiN x -treated GaN surface, to achieve high optical-quality QDs applicable for photonics devices.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2008
Publisher: IEEE
Date: 10-2015
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2005
Publisher: IEEE
Date: 12-2009
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2013
Publisher: Wiley
Date: 10-05-2012
Publisher: IEEE
Date: 09-2018
Publisher: IOP Publishing
Date: 24-07-2004
Publisher: Elsevier BV
Date: 04-2004
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2004
Publisher: MDPI AG
Date: 11-08-2020
DOI: 10.3390/MOLECULES25163646
Abstract: Graphene and its hybrids are being employed as potential materials in light-sensing devices due to their high optical and electronic properties. However, the absence of a bandgap in graphene limits the realization of devices with high performance. In this work, a boron-doped reduced graphene oxide (B-rGO) is proposed to overcome the above problems. Boron doping enhances the conductivity of graphene oxide and creates several defect sites during the reduction process, which can play a vital role in achieving high-sensing performance of light-sensing devices. Initially, the B-rGO is synthesized using a modified microwave-assisted hydrothermal method and later analyzed using standard FESEM, FTIR, XPS, Raman, and XRD techniques. The content of boron in doped rGO was found to be 6.51 at.%. The B-rGO showed a tunable optical bandgap from 2.91 to 3.05 eV in the visible spectrum with an electrical conductivity of 0.816 S/cm. The optical constants obtained from UV-Vis absorption spectra suggested an enhanced surface plasmon resonance (SPR) response for B-rGO in the theoretical study, which was further verified by experimental investigations. The B-rGO with tunable bandgap and enhanced SPR could open up the solution for future high-performance optoelectronic and sensing applications.
Publisher: AIP Publishing
Date: 13-09-2010
DOI: 10.1063/1.3489086
Abstract: Thermoelectric properties of lattice-matched AlInN grown by metal organic chemical vapor deposition were measured and analyzed. The n-type Al0.83In0.17N alloy exhibited thermal conductivity of 4.87 W/(m K) measured by 3ω differential method. The Seebeck coefficient of n-Al0.83In0.17N was measured as −6.012×10−4 V/K by thermal gradient method. The sheet resistivity of n-Al0.83In0.17N was measured by using Van der Pauw method, and the electrical conductivity was measured as 2.38×104/(Ω m). The thermoelectric figure of merit (Z∗T) of n-type Al0.83In0.17N was measured as 0.532 at room temperature (T=300 K). The finding indicates lattice-matched AlInN alloy on GaN as excellent material candidate for thermoelectric application.
Publisher: Elsevier
Date: 2011
Publisher: IEEE
Date: 11-2010
Publisher: AIP Publishing
Date: 25-04-2011
DOI: 10.1063/1.3583442
Abstract: The gain characteristics of high Al-content AlGaN-delta-GaN quantum wells (QWs) are investigated for mid- and deep-ultraviolet (UV) lasers. The insertion of an ultrathin GaN layer in high Al-content AlGaN QWs leads to valence subbands rearrangement, which in turn results in large optical gain for mid- and deep-UV lasers.
Publisher: The Optical Society
Date: 31-07-2013
DOI: 10.1364/AO.52.000HM1
Publisher: AIP Publishing
Date: 12-05-2005
DOI: 10.1063/1.1929880
Abstract: Gain properties of GaInNAs lasers with different nitrogen concentrations in the quantum wells are investigated experimentally and theoretically. Whereas nitrogen incorporation induces appreciable modifications in the spectral extension and the carrier density dependence of the gain, it is found that the linewidth enhancement factor is reduced by inclusion of nitrogen, but basically unaffected by different nitrogen content due to the balancing between gain and index changes.
Publisher: IEEE
Date: 11-2010
Publisher: IEEE
Date: 10-2007
Publisher: IEEE
Date: 11-2010
Publisher: AIP Publishing
Date: 16-08-2021
DOI: 10.1063/5.0057412
Abstract: A power figure-of-merit (FOM) of ∼62.6–87.3 GW/cm2 is predicted for ScAlN, which represents a value 5–7 times larger than that of GaN. The parameters for the lattice-matched Sc0.18Al0.82N FOM calculation are investigated by first-principles density functional theory (DFT) calculations with the local density approximation. An energy gap of 5.65 eV and an electron effective mass of 0.46m0 are obtained from the DFT band structure calculation of Sc0.1875Al0.8125N. The electron mobility of Sc0.18Al0.82N is simulated based on Boltzmann transport equations, which consider scatterings by ionized impurities, dislocations, alloy scattering, acoustic phonons, and optical phonons. The remarkable power FOM shows that lattice-matched Sc0.18Al0.82N possesses a large breakdown voltage and low specific on-resistance, which suggests the great potential for Sc0.18Al0.82N to be implemented in high-voltage power electronics for improved device performance.
Publisher: AIP Publishing
Date: 03-2017
DOI: 10.1063/1.4978777
Abstract: Auger recombination in a semiconductor is a three-carrier process, wherein the energy from the recombination of an electron and hole pair promotes a third carrier to a higher energy state. In semiconductor quantum wells with increased carrier densities, the Auger recombination becomes an appreciable fraction of the total recombination rate and degrades luminescence efficiency. Gaining insight into the variables that influence Auger recombination in semiconductor quantum wells could lead to further advances in optoelectronic and electronic devices. Here we demonstrate the important role that interface roughness has on Auger recombination within quantum wells. Our computational studies find that as the ratio of interface roughness to quantum well thickness is increased, Auger recombination is significantly enhanced. Specifically, when considering a realistic interface roughness for an InGaN quantum well, the enhancement in Auger recombination rate over a quantum well with perfect heterointerfaces can be approximately four orders of magnitude.
Publisher: Springer Science and Business Media LLC
Date: 16-04-2018
DOI: 10.1038/S41598-018-24384-1
Abstract: An investigation on the optical properties of dilute-P GaN 1−x P x alloys by First-Principle Density Functional Theory (DFT) methods is presented, for phosphorus (P) content varying from 0% up to 12.5%. Findings on the imaginary and real part of the dielectric function are analyzed and the results are compared with previously reported theoretical works on GaN. The complex refractive index, normal-incidence reflectivity and birefringence are presented and a difference in the refractive index in the visible regime between GaN and GaNP alloys of ~0.3 can be engineered by adding minute amounts of phosphorus, indicating strong potential for refractive index tunability. The optical properties of the GaN 1−x P x alloys indicate their strong potential for implementation in various III-nitride-based photonic waveguide applications and Distributed Bragg Reflectors (DBR).
Publisher: Wiley
Date: 2008
Publisher: AIP Publishing
Date: 22-08-2011
DOI: 10.1063/1.3627166
Publisher: IEEE
Date: 10-2017
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2018
Publisher: AIP Publishing
Date: 08-2016
DOI: 10.1063/1.4960375
Abstract: Here, we reveal a remarkable (and surprising) physical property of GaN: it is extremely wear resistant. In fact, we measured the wear rate of GaN is approaching wear rates reported for diamond. Not only does GaN have an ultralow wear rate but also there are quite a few experimental factors that control the magnitude of its wear rate, further contributing to the rich and complex physics of wear of GaN. Here, we discovered several primary controlling factors that will affect the wear rate of III-Nitride materials: crystallographic orientation, sliding environment, and coating composition (GaN, InN and InGaN). Sliding in the ⟨12¯10⟩ is significantly lower wear than ⟨11¯00⟩. Wear increases by 2 orders of magnitude with increasing humidity (from ∼0% to 50% RH). III-Nitride coatings are promising as multifunctional material systems for device design and sliding wear applications.
Publisher: OSA
Date: 2012
Publisher: SPIE
Date: 11-02-2010
DOI: 10.1117/12.841503
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2009
Publisher: IEEE
Date: 10-2011
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2011
Publisher: OSA
Date: 2012
Publisher: Elsevier BV
Date: 10-2010
Publisher: IEEE
Date: 05-2008
Publisher: SPIE-Intl Soc Optical Eng
Date: 23-10-2015
Publisher: AIP Publishing
Date: 23-10-2006
DOI: 10.1063/1.2364068
Abstract: A detailed line shape analysis of the temperature dependent photoluminescence spectra of In0.4Ga0.6As1−yNy∕GaAs quantum well (QW) (y=0,0.005) is carried out and the relative contribution of free excitons and free carriers to the radiative recombination at different temperature is quantitatively assessed. The analysis extracts the binding energy of the e1-hh1 ground-state exciton which equals 9.72±1.24 and 17.5±0.9meV for InGaAs and InGaAsN (N=0.5%) single QW s le, respectively. By using a fractional dimension exciton binding energy model, an electron effective mass of me*=(0.11±0.015)m0 is determined for the highly strained dilute nitride single QW.
Publisher: AIP Publishing
Date: 30-09-2003
DOI: 10.1063/1.1616193
Abstract: Whereas laser emission at 1.55 μm is difficult to realize using type-I InGaAsN quantum wells grown on GaAs, we show that it can be achieved with far fewer restrictions on the growth by employing type-II (In)GaAsN/GaAsSb/(In)GaAsN/GaAs structures having a “W” band alignment. We use a 10-band k⋅p formalism that accounts for the N band anticrossing to calculate the gain and spontaneous-emission characteristics of “W” structures optimized for maximum overlap of the electron and hole wave functions. We estimate that one to three wells would be necessary for edge emitters with moderate cavity losses and nonradiative recombination rates, and a somewhat larger number of wells may be required for vertical-cavity surface emitters.
Publisher: IEEE
Date: 09-2018
Publisher: IEEE
Date: 10-2017
Publisher: OSA
Date: 2010
Publisher: Elsevier BV
Date: 10-2020
Publisher: IEEE
Date: 10-2017
Publisher: OSA
Date: 2011
Publisher: IEEE
Date: 10-2017
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2000
DOI: 10.1109/68.849057
Publisher: IEEE
Date: 08-2012
Start Date: 04-2022
End Date: 04-2025
Amount: $460,000.00
Funder: Australian Research Council
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