ORCID Profile
0000-0002-3985-6768
Current Organisation
Nanjing University
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Plant Cell and Molecular Biology | Plant Biology | Plant Physiology |
Plant Production and Plant Primary Products not elsewhere classified | Expanding Knowledge in the Biological Sciences
Publisher: AIP Publishing
Date: 11-2021
DOI: 10.1063/5.0068813
Abstract: Heteroepitaxy of corundum-structured α-Ga2O3 and intriguing ferroelectric κ-Ga2O3 is proven as an alternative strategy to solve current challenges in heat dissipation and large-scale productivity for Ga2O3-based power electronic devices, whereas the fundamental growth dynamics and phase control of metastable Ga2O3 are still far unexplored. In this Letter, we demonstrate the strategy of strain engineering for the in situ phase manipulation of metastable Ga2O3 by embedding α-In2O3 submicrometer dots. Phase transition is modulated by the surface coverage of α-In2O3 due to the competitive growth of κ-Ga2O3 upon α-In2O3 and the homoepitaxy of α-Ga2O3 on the exposed α-Ga2O3 seed region. Upon discrete α-In2O3 submicrometer dots with a low surface coverage, the growth undergoes a nano-scale epitaxial lateral overgrowth mode, in which the selective homoepitaxy of α-Ga2O3 is dominant, and embedded α-In2O3 serves as nano-masks to prevent the threading dislocation propagation into the lateral overgrown Ga2O3 layer. In comparison, κ-Ga2O3 is energetically favorable on the interconnected α-In2O3 submicrometer dots, which are driven by the in-plane tensile strain as probed by the geometric phase analysis of transmission electron microscopy. Phase manipulation by embedded sub micrometer dots allows us to deliver high-quality Ga2O3 with well-defined phases and to conceive advanced devices with ultra-low loss, high frequency, and memorizing functionality.
Publisher: AIP Publishing
Date: 04-10-2021
DOI: 10.1063/5.0059061
Abstract: In this work, we demonstrated the self-powered solar-blind photodetector based on a polyaniline/α-Ga2O3 hybrid heterojunction. The resultant device exhibited distinct self-power characteristics with a peak photoresponsivity (R) of 8.2 mA/W, a UVC (UV light of wavelength range at 200–280 nm)/UVA (UV light of wavelength range at 320–400 nm) rejection ratio (R220 nm/R400 nm) of 2.97 × 104, and a response decay time (τdec) of 176 μs at zero bias. With an elevated bias to 5 V, the dark current remained in an ultralow level of 0.21 pA, while the rejection ratio and τdec were improved to be 7.13 × 104 and 153 μs, respectively, together with the corresponding external quantum efficiency of 38.4% and a detectivity of 6.63 × 1013 Jones. Thanks to the dual functions of bandpass transmission in the deep-ultraviolet spectral region and the hole spreading transport of the polyaniline layer, the responsivity to the visible light is suppressed with the negligible internal photoemission effect, thus leading to the improved rejection ratio. Furthermore, weak interface interactions in such polyaniline/α-Ga2O3 organic–inorganic hybrid systems avoid the introduction of interfacial trapping centers by lattice mismatch and the stabilization of negatively charged anions (O2−) by (−NH2)-+species in polyaniline deactivate oxygen vacancies at the α-Ga2O3 surface, both of which lead to the negligible persistent photoconductivity effect. As a result, in the aid of the interfacial built-in field, the constructed hybrid heterojunction exhibited a self-powered detecting characteristic and a fast response speed. These findings verify the feasibility of delivering high performance photodetectors by implementing the inorganic/organic hybrid bipolar device design to overcome the difficulty in p-type Ga2O3.
Publisher: AIP Publishing
Date: 28-06-2021
DOI: 10.1063/5.0047710
Abstract: The construction of Ga2O3-based p-n heterojunction offers an alternative strategy to realize bipolar power devices however, lattice mismatch usually leads to undesirable device performance and makes interface engineering more challenging. In this work, we demonstrated the construction of lattice-matched p-n heterojunctions by the in situ hetero-epitaxy of p-type α-Ir2O3 on n-type Si-doped α-Ga2O3 using the mist-chemical vapor deposition technique. The α-Ga2O3/α-Ir2O3 p-n heterojunction shows single-crystalline corundum structures and well-defined rectifying characteristics. The transport mechanism has been identified to be space-charge-limited current conduction, which is induced by interfacial traps in an ultrathin disordered layer at the α-Ga2O3/α-Ir2O3 interface. Through thermal treatment in oxygen ambient, interfacial trapping states are suppressed, and more shallow acceptors of Ir vacancies are activated, both of which lead to the profound reduction of reverse leakage current, thus the improved current rectification ratio. The p-type α-Ir2O3 with advantages of lattice matching to α-Ga2O3 provides a promising strategy to realize high-performance bipolar power devices.
Publisher: Optica Publishing Group
Date: 02-01-2023
DOI: 10.1364/OL.478848
Abstract: The authors demonstrate the enhanced light output from 275-nm AlGaN-based deep ultraviolet (DUV) light-emitting diode (LED) structures via the in-plane modulation of shallow photonic crystal (PC) patterns that were fabricated on the p-AlGaN contact layer surface. The employed PC lattice constants are in the range of 270–780 nm, much larger than the fundamental Bragg order lattice constant (∼95 nm). As compared to the unpatterned s le, the intensity of the top (or bottom) emission can be enhanced by up to 331% (or 246%), attributed to the high-order coherent diffraction of the internal trapped light and also the Purcell enhancement of spontaneous emission. The findings in this Letter suggest an easier way for the realization of more energy-efficient DUV LEDs which offer the advantage of high emission for various applications in disinfection and sterilization.
Publisher: AIP Publishing
Date: 21-12-2020
DOI: 10.1063/5.0028760
Abstract: The generation of p-type GaN through ion implantation is an attractive proposition in the massive production of GaN-based bipolar devices, whereas the removal of implantation induced lattice disturbances and defects is a difficult exercise and h ers the conversion of conductivity in GaN. Pulsed laser annealing is an effective annealing technique to recover lattice crystallinity and activate dopants with the preserved implanted profile. In this work, the effect of pulsed laser annealing on structural and optical recovery in high-dose magnesium (Mg) ion-implanted GaN has been investigated. The structural evolution and vibrational dynamics indicate an obvious structural recovery and partial strain release of Mg-implanted GaN during the pulsed laser annealing process, with a threshold laser fluence of 400 mJ/cm2, while rough surface structures are a result of the regrowth mechanism similar to liquid phase epitaxy. The enhanced donor–acceptor transition at 3.35 eV after pulsed laser irradiation is a sign of the effective activation of Mg from interstitial sites into the substitution of Ga ions. These results suggest that further optimization of the laser annealing technique has promising potential to manipulate the p-type conductivity of Mg-implanted GaN and to be implemented in GaN bipolar devices for practical applications.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2020
Publisher: AIP Publishing
Date: 11-11-2019
DOI: 10.1063/1.5126325
Abstract: Understanding the electronic structures at the interfaces of wide bandgap oxide heterostructures is crucial for the rational design of oxide-based optoelectronic devices with novel functionality and improved performance. In this work, the electronic band diagram at a ZnO/α-Ga2O3 n-n isotype heterojunction is investigated by depth-profile x-ray photoemission spectroscopy (XPS). The directly measured valence-band offset is −0.61 ± 0.1 eV and a type-I (straddling gap) band alignment is formed at the ZnO/α-Ga2O3 heterointerface. As probed by the depth profile of core-levels and VB-XPS, the formation of an interfacial layer is observed due to Ga and Zn interdiffusion, where charged interfacial states result in the downward and upward band-bending at the ZnO and α-Ga2O3 sides, respectively. The influence of band bending and band discontinuity at the interface is confirmed by the rectifying characteristics in the Au/α-Ga2O3/ZnO heterojunction with electron accumulation at its interface. Taking the thermionic-field emission and band-to-band tunneling mechanisms into account, the simulated transport properties agrees well with the reported I-V characteristics of Au/α-Ga2O3/ZnO avalanche photodiode, a further validation of the deduced band alignment of the heterostructure.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2021
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2022
Publisher: American Chemical Society (ACS)
Date: 28-07-2022
DOI: 10.1021/ACS.JPCLETT.2C02167
Abstract: Surface treatment after dry etching is vital to enhance the surface quality of the material and thus improve device performance. In this Letter, we identified the majority surface states induced by the dry etching of β-Ga
Publisher: IOP Publishing
Date: 17-01-2020
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: IOP Publishing
Date: 24-05-2019
Publisher: IOP Publishing
Date: 21-07-2022
Abstract: The metal-semiconductor-metal (MSM) structure is a popular architecture for developing Ga 2 O 3 solar blind photodetectors. The nature of metal-semiconductor contact is decisive for the operation mode, gain mechanism and device performances. In this contribution, κ -Ga 2 O 3 MSM solar-blind photodetectors with Ti/Ga 2 O 3 Ohmic and Ni/Ga 2 O 3 Schottky contacts were constructed on the high-quality Si-doped κ -Ga 2 O 3 epilayer grown by hydride vapor phase epitaxy. The Ti/ κ -Ga 2 O 3 /Ti Ohmic MSM device is operated in a photoconductive mode, exhibiting a maximum responsivity of 322.5 A W −1 and a high rejection ratio of over 10 5 , but with an undesirable sub-gap response and high dark current. In comparison, the Ni/Ga 2 O 3 /Ni photodiode with a back-to-back Schottky configuration is operated in a mixed photovoltaic and photoconductive mode, demonstrating a decent photoresponsivity of 0.37 A W −1 , a maintained high rejection ratio of 1.16 × 10 5 , a detectivity of 3.51 × 10 13 Jones and the elimination of slow photoresponse from sub-gap states. The frequency-dependent photoresponse and transient photocurrent characteristics indicate that the persistent photoconductivity effect is responsible for the high gain achieved in the Ti/Ga 2 O 3 /Ti photoconductor, and the dominant slow transient decay component is a fingerprint of photoexcited carrier trapping and repopulation. The response speed is improved in the Ni/Ga 2 O 3 /Ni Schottky MSM device, whereas carrier transport across interdigitated fingers is affected by bulk traps, limiting the overall response-bandwidth merit.
Publisher: IOP Publishing
Date: 13-12-2018
Abstract: ZnO nanowire photodetectors have attracted much attention due to their excellent optoelectronic performance. However, operating speed remains a challenge, and scalability is also impeded by uncontrolled transfer methods and sophisticated fabrication process. In this paper, we have fabricated an excellent ZnO nanobridge ultraviolet photodetector array by using a simple one-step method. The faster photoresponse speed and a broader response wavelength (from UV to visible range) have been achieved by constructing a type-II ZnO/rubrene heterointerface. Performance enhancement is believed to arise from the well-matching band alignment and highly efficient separation of photogenerated electron-hole pairs at the heterointerface. Our strategy provides a simple and promising route to develop cost-effective and highly sensitive UV-vis photodetectors.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 02-2022
Publisher: IOP Publishing
Date: 11-04-2023
Abstract: Single-photon emitters based on intrinsic defects in silicon carbide (SiC) are promising as solid-state qubits for the quantum information storage, whereas defect engineering in a controllable manner still remains challenging. Herein, the thermally-driven defect dynamic reaction in the ion implanted 4H-SiC has been exploited through the optical emission spectra of defects. For the heavy-ion (Si or Ar) implanted s les with abundant Frenkel pairs, the silicon vacancies (V Si ) are energetically converted into the carbon antisite-vacancy pair (C Si -V C ) upon annealing till 1300 °C for 30 min, accompanied with the gradual lattice recovery and local strain relaxation. The further temperature elevation dissociates the metastable C Si -V C into carbon antisite (C Si ) and carbon vacancy (V C ), as supported by the consequent quenching of the (C Si -V C )-related emission at 700 nm. Thus, the whole defect reaction is probed as the vacancy interconversion from V Si to V C with the byproduct of stacking faults. In contrast, the intermediate C Si -V C complexes are not energetically favorable during the annealing of the H-implanted s le, which results from the negligible generation of Frenkel pairs, as supported by the x-ray diffraction patterns and Raman scattering analysis. These findings provide guidance for defect engineering in SiC toward the creation of reliable single photon emitters.
Publisher: IOP Publishing
Date: 03-11-2020
Abstract: As an ultrawide bandgap semiconductor, gallium oxide (Ga 2 O 3 ) has superior physical properties and has been an emerging candidate in the applications of power electronics and deep-ultraviolet optoelectronics. Despite numerous efforts made in the aspect of material epitaxy and power devices based on β -Ga 2 O 3 with rapid progresses, the fundamental understanding of defect chemistry in Ga 2 O 3 , in particular, acceptor dopants and carrier compensation effects, remains a key challenge. In this focused review, we revisited the principles of popular approaches for characterizing defects in semiconductors and summarized recent advances in the fundamental investigation of defect properties, carrier dynamics and optical transitions in Ga 2 O 3 . Theoretical and experimental investigations revealed the microstructures and possible origins of defects in β -Ga 2 O 3 bulk single crystals, epitaxial films and metastable-phased α -Ga 2 O 3 epilayers by the combined means of first-principle calculation, deep level transient spectroscopy and cathodoluminescence. In particular, defects induced by high-energy irradiation have been reviewed, which is essential for the identification of defect sources and the evaluation of device reliability operated in space and other harsh environments. This topic review may provide insight into the fundamental properties of defects in Ga 2 O 3 to fully realize its promising potential in practical applications.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2023
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2023
Publisher: IOP Publishing
Date: 12-12-2019
Publisher: AIP Publishing
Date: 13-07-2015
DOI: 10.1063/1.4926854
Abstract: ZnO hybrid materials with singly precipitated ZnO nanocrystals embedded in the glass surface were fabricated by melt-quenching method followed by the annealing process. A series of s les containing different densities and species of intrinsic defects were obtained under different annealing conditions in a controllable manner, which was an ideal platform to identify the complicated defect origins. By employing photoluminescence (PL), excitation-dependent PL, PL excitation (PLE), and Raman spectroscopy, the radiative transitions of visible emission bands at around 401, 490, and 528 nm were unambiguously involved with zinc interstitial-related defect levels as initial states, and the corresponding terminal states were suggested to be valence band, oxygen vacancies, and zinc vacancies, respectively. This study may deepen the fundamental understanding of defect-related emissions and physics in ZnO and benefit potential applications of ZnO hybrid materials in optoelectronics.
Publisher: IOP Publishing
Date: 07-02-2018
Abstract: Recently, ZnO nanowire field effect transistors (FETs) have received renewed interest due to their extraordinary low dimensionality and high sensitivity to external chemical environments and illumination conditions. These prominent properties have promising potential in nanoscale chemical and photo-sensors. In this article, we have fabricated ZnO nanowire FETs and have found hysteresis behavior in their transfer characteristics. The mechanism and dynamics of the hysteresis phenomena have been investigated in detail by varying the sweeping rate and range of the gate bias with and without light irradiation. Significantly, light irradiation is of great importance on charge trapping by regulating adsorption and desorption of oxygen at the interface of ZnO/SiO
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2020
Publisher: IOP Publishing
Date: 22-10-2021
Publisher: Optica Publishing Group
Date: 16-05-2023
DOI: 10.1364/OE.488330
Abstract: Ultraviolet photodetectors have aroused wide concern based on wide-band-gap semiconductors, such as GaN and Ga 2 O 3 . Exploiting multi-spectral detection provides unparalleled driving force and direction for high-precision ultraviolet detection. Here we demonstrate an optimized design strategy of Ga 2 O 3 /GaN heterostructure bi-color ultraviolet photodetector, which presents extremely high responsivity and UV-to-visible rejection ratio. The electric field distribution of optical absorption region was profitably modified by optimizing heterostructure doping concentration and thickness ratio, thus further facilitating the separation and transport of photogenerated carriers. Meanwhile, the modulation of Ga 2 O 3 /GaN heterostructure band offset leads to the fluent transport of electrons and the blocking of holes, thereby enhancing the photoconductive gain of the device. Eventually, the Ga 2 O 3 /GaN heterostructure photodetector successfully realizes dual-band ultraviolet detection and achieves high responsivity of 892/950 A/W at the wavelength of 254/365 nm, respectively. Moreover, UV-to-visible rejection ratio of the optimized device also keeps at a high level (∼10 3 ) while exhibiting dual-band characteristic. The proposed optimization scheme is anticipated to provide significant guidance for the reasonable device fabrication and design on multi-spectral detection.
Publisher: The Optical Society
Date: 19-11-2018
DOI: 10.1364/OE.26.031965
Publisher: AIP Publishing
Date: 02-12-2019
DOI: 10.1063/1.5126930
Abstract: Bandgap engineering of gallium zinc oxynitride (GaZnON) thin films has been performed by the GaN/ZnO pseudobinary alloying in a periodical superlattice order through the pulsed laser deposition technique. By tuning the growth temperature, the combined engineering of anions and cations in GaZnON quaternary alloys leads to a large tunability of the optical bandgap from 1.80 to 4.34 eV. In terms of the enthalpy of formation and kinetic dynamics of reactant species, nitrogen incorporation is effective to form Zn3N2-rich GaZnON quaternary alloys at low-temperature (& °C) conditions far from the equilibrium, while amorphous nitrogen deficient GaZnON is formed at high temperatures with ZnGa2O4 and β-Ga2O3 nanocrystalline structures embedded. The conduction band (CB) and valence band (VB) of GaZnON are determined by Zn 4s orbital electrons and the hybridization of N 2p and O 2p electrons, respectively, while the Ga 4s and O 2p are predominant to construct the CB and VB of O-rich GaON due to the low solubility of N at high temperature. The asymmetric band bowing effect of GaZnON quaternary alloy demonstrates a large bandgap tunability down to the visible spectral range, which provides significant potential applications in the harvest of solar energy technologies.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2022
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2022
Publisher: AIP Publishing
Date: 13-07-2020
DOI: 10.1063/5.0009615
Abstract: In this work, sulfur addition has been employed on the boron-doped diamond growth process, and a significant regulation of the boron doping and the growth behavior has been realized by microwave plasma chemical vapor deposition. It is interesting to find that the sulfur incorporation will lead to an accordant evolution on the boron doping efficiency, hole mobility and concentration, crystal quality, surface morphology, and growth rate. In the presence of sulfur with appropriate dosage, for a boron-to-carbon ratio of only 2.5 ppm in gas phase during growth, a very high doping concentration of 1.2 × 1019 at/cm3 has been achieved, indicative of a very efficient boron doping. Besides, the hole mobility of the s le is 853 cm2/V s at 300 K, which is better than the state of the art for p-type doping in diamond. The regulation mechanism of the sulfur addition will be discussed from the point of view of sulfur-induced plasma change and possible B–S complex formation. This study may provide an effective way for high-quality p-type conductive diamond layer growth and further for the potential diamond-based opto-electronic device applications.
Publisher: IOP Publishing
Date: 28-07-2020
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2020
Publisher: AIP Publishing
Date: 28-10-2019
DOI: 10.1063/1.5120554
Abstract: Epitaxial film quality is critical to the success of high-performance α-Ga2O3 vertical power devices. In this work, the origins of threading dislocation generation and annihilation in thick α-Ga2O3 films heteroepitaxially grown on sapphire by the mist-CVD technique have been examined by means of high-resolution X-ray diffraction and transmission electron microscopies. By increasing the nominal thickness, screw dislocations exhibit an independent characteristic with a low density of about 1.8 × 106 cm−2, while edge dislocations propagating along the c-axis are dominant, which decrease down to 2.1 × 109 cm−2 in density for an 8 μm-thick α-Ga2O3 layer and exhibit an inverse dependence on the thickness. In the framework of the glide analytical model, parallel edge dislocations are generated at the interface due to the misfit-induced strain relaxation, while the dislocation glide and coalescence result in the annihilation and fusion behaviors. The optimal thick α-Ga2O3 with low dislocation densities may provide a prospective alternative to fully realize α-Ga2O3 power devices.
Publisher: American Chemical Society (ACS)
Date: 18-01-2021
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2019
Publisher: AIP Publishing
Date: 13-07-2020
DOI: 10.1063/5.0010052
Abstract: In this Letter, high-performance vertical NiO/β-Ga2O3 p–n heterojunction diodes without any electric field managements were reported. The devices show a low leakage current density and a high rectification ratio over 1010 (at ±3 V) even operated at temperature of 400 K, indicating their excellent thermal stability and operation capability at high temperature. Given a type-II band alignment of NiO/β-Ga2O3, carrier transport is dominated by the interface recombination at forward bias, while the defect-mediated variable range hopping conduction is identified upon strong reverse electric field. By using the double-layer design of NiO with a reduced hole concentration of 5.1 × 1017 cm−3, the diode demonstrates an improved breakdown voltage (Vb) of 1.86 kV and a specific on-resistance (Ron,sp) of 10.6 mΩ cm2, whose power figure of merit (Vb2/Ron,sp) has reached 0.33 GW/cm2. The high breakdown voltage and low leakage current are outperforming other reported Ga2O3 based p–n heterojunctions and Schottky barrier diodes without field plate and edge termination structures. TCAD simulation indicates that the improved Vb is mainly attributed to the suppression of electric field crowding due to the decreased hole concentration in NiO. Such bipolar heterojunction is expected to be an alternative to increase the breakdown characteristics of β-Ga2O3 power devices.
Publisher: Optica Publishing Group
Date: 14-02-2020
DOI: 10.1364/OE.380017
Abstract: Enhancement in the light interaction between plasmonic nanoparticles (NPs) and semiconductors is a promising way to enhance the performance of optoelectronic devices beyond the conventional limit. In this work, we demonstrated improved performance of Ga 2 O 3 solar-blind photodetectors (PDs) by the decoration of Rh metal nanoparticles (NPs). Integrated with Rh NPs on oxidized Ga 2 O 3 surface, the resultant device exhibits a reduced dark current of about 10 pA, an obvious enhancement in peak responsivity of 2.76 A/W at around 255 nm, relatively fast response and recovery decay times of 1.76 ms/0.80 ms and thus a high detectivity of ∼10 13 Jones. Simultaneously, the photoresponsivity above 290 nm wavelength decreases significantly with improved rejection ratio between ultraviolet A (UVA) and ultraviolet B (UVB) regions, indicative of enhanced wavelength detecting selectivity. The plasmonic resonance features observed in transmittance spectra are consistent with the finite difference time-domain (FDTD) calculations. This agreement indicates that the enhanced electric field strength induced by the localized surface plasmon resonance is responsible for the enhanced absorption and photoresponsivity. The formed localized Schottky barrier at the interface of Rh/Ga 2 O 3 will deplete the carriers at the Ga 2 O 3 surface and lead to the remarkable reduced dark current and thus improve the detectivity. These findings provide direct evidence for Rh plasmonic enhancement in solar-blind spectral region, offering an alternative pathway for the rational design of high-performance solar-blind PDs.
Publisher: IOP Publishing
Date: 03-10-2022
Abstract: The application of p-type oxide typified with NiO x as cap layer in AlGaN/GaN high electron mobility transistor for normally-off operation has specific benefits, including etching free fabrication process, high hole density and elimination of Mg dopants diffusion effects. This work presents a device configuration exploration combining the p-NiO x gate cap layer and a thin AlGaN barrier layer. Calculation method for the threshold voltage has been discussed, which obtains good consistence with the experimental measurements. In addition, a nitrogen based post-annealing process was developed to improve the film stoichiometry for elevated gate controllability, realizing normally-off operation with enhanced channel conduction capability. The current transport dynamics in the gate stack as coupled with the NiO x /AlGaN interface states have also been studied, where a deep level trap was recognized in dominating the gate current characteristics and the gate stability performance under different forward gate bias conditions.
Publisher: American Chemical Society (ACS)
Date: 06-02-2020
Publisher: AIP Publishing
Date: 08-09-2020
DOI: 10.1063/5.0021344
Abstract: In this Letter, we report on the evolution of electronic properties governed by epitaxial misfit strain in cubic In2O3 epilayers grown on sapphire. At elevated growth temperature, the competition between the film/substrate lattice mismatch and the thermal expansion mismatch alters the macroscopic biaxial strain from compressive to tensile. Simultaneously, the electron concentration is tuned from degeneration to non-degeneration density below the Mott criterion. The observed surface electron accumulation and metal-insulator transition result from the oxygen deficiency formed at low growth temperature, while high-temperature epitaxy is favorable to achieve remarkably enhanced mobility. The effective strain-property coupling suggests that the improved oxygen stoichiometry and the Fermi level movement controlled by the biaxial strains are responsible for the Mott transition. The strain-mediated reduction of the electron effective mass contributes to the enhanced intrinsic mobility in tensile-strained In2O3 epilayers. These results highlight that strain engineering is an effective stimulus to manipulate the transport properties of oxide semiconductors with improved performance and unexpected functionalities.
Publisher: American Chemical Society (ACS)
Date: 26-05-2022
Publisher: Optica Publishing Group
Date: 26-09-2022
DOI: 10.1364/PRJ.465401
Abstract: Pursuing nanometer-scale nonlinear converters based on second harmonic generation (SHG) is a stimulating strategy for bio-sensing, on-chip optical circuits, and quantum information processing, but the light-conversion efficiency is still poor in such ultra-small dimensional nanostructures. Herein, we demonstrate a highly enhanced broadband frequency converter through a hybrid plasmonic–dielectric coupler, a ZnTe/ZnO single core–shell nanowire (NW) integrated with silver (Ag) nanoparticles (NPs). The NW dimension has been optimized to allow the engineering of dielectric resonances at both fundamental wave and second harmonic frequencies. Meanwhile, the localized surface plasmon resonances are excited in the regime between the Ag NPs and ZnTe/ZnO dielectric NW, as evidenced by plasmon-enhanced Raman scattering and resonant absorption. These two contributors remarkably enhance local fields and consequently support the strong broadband SHG outputs in this hybrid nanostructure by releasing stringent phase-matching conditions. The proposed nanoscale nonlinear optical converter enables the manipulation of nonlinear light–matter interactions toward the development of on-chip nanophotonic systems.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2022
Publisher: American Chemical Society (ACS)
Date: 12-01-2021
Publisher: Springer Science and Business Media LLC
Date: 25-07-2023
DOI: 10.1038/S41467-023-40194-0
Abstract: Avalanche and surge robustness involve fundamental carrier dynamics under high electric field and current density. They are also prerequisites of any power device to survive common overvoltage and overcurrent stresses in power electronics applications such as electric vehicles, electricity grids, and renewable energy processing. Despite tremendous efforts to develop the next-generation power devices using emerging ultra-wide bandgap semiconductors, the lack of effective bipolar doping has been a daunting obstacle for achieving the necessary robustness in these devices. Here we report avalanche and surge robustness in a heterojunction formed between the ultra-wide bandgap n-type gallium oxide and the wide-bandgap p-type nickel oxide. Under 1500 V reverse bias, impact ionization initiates in gallium oxide, and the staggered band alignment favors efficient hole removal, enabling a high avalanche current over 50 A. Under forward bias, bipolar conductivity modulation enables the junction to survive over 50 A surge current. Moreover, the asymmetric carrier lifetime makes the high-level carrier injection dominant in nickel oxide, enabling a fast reverse recovery within 15 ns. This heterojunction breaks the fundamental trade-off between robustness and switching speed in conventional homojunctions and removes a key hurdle to advance ultra-wide bandgap semiconductor devices for power industrial applications.
Publisher: AIP Publishing
Date: 08-2021
DOI: 10.1063/5.0049151
Abstract: The n-type doping of diamond is quite difficult, hindering the development of diamond-based electronic devices for decades. In this work, we have designed a boron–nitrogen co-doping technique to realize n-type diamonds. Basically, the activation energy of the donors has been greatly reduced by around 50%, thanks to the successful synthesis of the boron–nitrogen related donor-like complex by a fine control of the synthesis condition. Compared to the sole nitrogen doping scheme, it is found that the co-incorporation of boron elements is beneficial to a lot of aspects, including better crystalline quality, faster growth, higher nitrogen solubility, and stability. With the technique, a p-i-n diamond homojunction has been fabricated. A clear rectification behavior has been recorded, demonstrating that the current co-doping technique we proposed is a feasible path to the accessible n-type diamond.
Publisher: The Optical Society
Date: 15-07-2019
DOI: 10.1364/PRJ.7.000B48
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 11-2021
Publisher: IOP Publishing
Date: 14-10-2020
Abstract: AlGaN/GaN high electron mobility transistors (HEMTs) have demonstrated their extraordinary potential in developing solid-state microsensors for detecting gases, metal ions, anions, biomolecules, and other substances due to their excellent chemical stability, high surface charge sensitivity, high temperature-tolerance performance, and low power consumption characteristics. In this paper, only three types of AlGaN/GaN HEMT-based sensors used for detecting the p H value, heavy metal ions, and harmful anions, which are suitable for water quality monitoring, will be discussed. First, we introduce the structural design, detection principle, and fabrication processes of AlGaN/GaN HEMT-based sensors. Then, surface functionalization methods for the gate region, sensing mechanisms, and the sensitivity and selectivity performances based on different gate region treatments are reviewed and analyzed. Finally, some challenging problems that hinder the practical application of the sensors are proposed.
Publisher: AIP Publishing
Date: 21-10-2021
DOI: 10.1063/5.0059841
Abstract: Normally off AlGaN/GaN high electron mobility transistors with a p-type gate are promising for power switching applications, with advantages of low energy consumption and safe operation. In this work, p-NiO is employed as a gate stack, and the interfacial reconstruction and band structure modification at the p-NiO/AlGaN interface have been demonstrated to manipulate channel transport of AlGaN/GaN high electron mobility transistors by post-annealing. In addition to achieving a positive threshold voltage of 0.6 V and a large saturation output current of 520 mA/mm, we found that the gate leakage and On/Off drain current ratio can be improved significantly by more than 104 due to the p-NiO/AlGaN interfacial reconstruction. However, high annealing temperature also results in an increasing ON-resistance and a dramatically increased knee voltage (VK), which can be attributed to the formation of an ultra-thin γ-Al2O3 layer and the substitution of O on N site as a shallow donor at the p-NiO/AlGaN interface confirmed by experimental analyses. Theoretical calculations indicate that such interface reconstruction facilitates an additional potential well at the p-NiO/AlGaN interface to which electrons are spilled out from a two-dimensional electron gas channel under high forward gate voltage, resulting in the increased VK. Finally, an optimized annealing condition was confirmed that can eliminate this increased VK phenomenon and simultaneously remain these significantly improved device performances. These findings provide deep understanding of the performance manipulation of AlGaN high electron mobility transistors, which is very important for engineering the p-NiO/AlGaN interface toward high-performance and stable devices.
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: American Chemical Society (ACS)
Date: 25-03-2022
Publisher: American Chemical Society (ACS)
Date: 11-10-2017
Abstract: The metastable α-phase Ga
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2021
Publisher: American Chemical Society (ACS)
Date: 03-10-2019
Abstract: In this work, nanoplasmonically enhanced α-Ga
Publisher: AIP Publishing
Date: 15-08-2022
DOI: 10.1063/5.0098610
Abstract: In this Letter, we report on the enhanced radio frequency (RF) performance in sub-micrometer scaled β-Ga2O3 tri-gate FinFETs. With a 200-nm-thick β-Ga2O3 bulk channel and a 0.35 μm gate length, the FinFETs exhibit an improved current-gain cutoff frequency of 5.4 GHz and a maximum oscillation frequency of 11.4 GHz, which are 20% and 58% improved with respect to the planar counterpart, respectively. The improved RF performance results from the enhanced gate control capability and the suppressed short-channel effects, as evidenced by the improved pinch-off characteristics, the improved transconductance, and the suppressed output conductance. It suggests that the tri-gate multi-fin architecture is a promising strategy to break the scaling limitation of the gate-channel aspect ratio toward high-performance β-Ga2O3 RF MOSFETs.
Publisher: AIP Publishing
Date: 17-05-2021
DOI: 10.1063/5.0050919
Abstract: In this Letter, high-performance β-Ga2O3 vertical heterojunction barrier Schottky (HJBS) diodes have been demonstrated together with the investigation of reverse leakage mechanisms. In HJBS configurations, NiO/β-Ga2O3 p-n heterojunctions and p-NiO field limiting rings (FLRs) are implemented by using a reactive sputtering technique at room temperature without intentional etching damages. Determined from the temperature-dependent current-voltage characteristics, the reverse leakage mechanism of the HJBS diode is identified to be Poole-Frenkel emission through localized trap sates with an energy level of EC-0.72 eV. With an uniform FLR width/spacing of 2 μm in HJBS, a maximum breakdown voltage (BV) of 1.89 kV and a specific on-resistance (Ron,sp) of 7.7 mΩ·cm2 are achieved, yielding a high Baliga's figure-of-merit (FOM, BV2/Ron,sp) of 0.46 GW/cm2. The electric field simulation and statistical experimental facts indicate that the electric field crowding effect at device edges is greatly suppressed by the shrinkage of p-NiO FLR spacing, and the capability of sustaining high BV is enhanced by the NiO/β-Ga2O3 bipolar structure, both of which contribute to the improved device performance. This work makes a significant step to achieve high performance β-Ga2O3 power devices by implementing alternative bipolar structures to overcome the difficulty in p-type β-Ga2O3.
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: American Chemical Society (ACS)
Date: 20-12-2021
Publisher: American Chemical Society (ACS)
Date: 13-07-2022
Publisher: AIP Publishing
Date: 28-02-2022
DOI: 10.1063/5.0082377
Abstract: This work acquires a vertical β-Ga2O3 Schottky barrier diode (SBD) with the advanced termination structure of p-type NiOx and n-type β-Ga2O3 heterojunctions and coupled field plate structures to alleviate the crowding electric field. A Ga2O3 SBD delivers an average breakdown voltage of 1860 V and a specific on-resistance of 3.12 mΩ cm2, yielding a state-of-the-art direct-current Baliga's power figure of merit of 1.11 GW/cm2 at an anode area of 2.83 × 10−5 cm2. In addition, the Ga2O3 SBD with the same fabrication process at a large area of 1.21 × 10−2 cm2 also presents a high forward current of 7.13 A, a breakdown voltage of 1260 V, and a power figure-of-merit of 235 MW/cm2. According to dynamic pulse switching and capacitance-frequency characteristics, an optimized p-NiOx/Ga2O3 interface with a maximum trap density of 4.13 × 1010 eV−1 cm−2 is delivered. Moreover, based on the forward current-voltage measurement at various temperatures, the physics behind a forward conduction mechanism is illustrated. Ga2O3 SBDs with p-NiOx/n-Ga2O3 heterojunction termination, field plate, high power figure of merit, and high quality interface as well as suppressed resistance increase after dynamic pulse switching, verifying their great promise for future high power applications.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2022
Publisher: IOP Publishing
Date: 23-02-2023
Abstract: Metal-semiconductor-metal (MSM) architectures are popular for achieving high-responsivity Ga 2 O 3 solar-blind photodetectors (SBPDs), however, the hot-electron-induced internal photoemission (IPE) effect restricts their detecting performance. Herein, we demonstrate the rational design of an Al/Al 2 O 3 /Ga 2 O 3 metal–insulator-semiconductor (MIS) SBPD that has merits of enhanced responsivity, suppressed sub-gap response and ultralow dark current based on the simulation results obtained using Lumerical software. For the cylindrical patterned detectors with Al/Al 2 O 3 /Ga 2 O 3 MIS structures, the optimized dimensions of Al electrodes with a conformed ultra-thin (2 nm) Al 2 O 3 layer support the surface plasmon polariton resonances at 250 nm, thus improving the photoresponsivity to 74 mA W −1 . Furthermore, the sandwiched Al 2 O 3 layer lifts the barrier for hot electrons in electrodes, which significantly suppresses the IPE-induced sub-gap photoresponse by more than 10 5 in magnitude with respect to the Al/Ga 2 O 3 MSM counterpart. Optical and electrical field distributions are overlapped in cylindrically patterned MIS detectors, simultaneously improving the excitation and collection efficiencies of excess carriers and resulting in the 10 3 -boosted rejection ratio.
Publisher: AIP Publishing
Date: 22-03-2021
DOI: 10.1063/5.0044130
Abstract: In this paper, we show that high-performance β-Ga2O3 hetero-junction barrier Schottky (HJBS) diodes with various β-Ga2O3 periodic fin widths of 1.5/3/5 μm are demonstrated with the incorporation of p-type NiOx. The β-Ga2O3 HJBS diode achieves a low specific on-resistance (Ron,sp) of 1.94 mΩ cm2 with a breakdown voltage of 1.34 kV at a β-Ga2O3 periodic fin width of 3 μm, translating to a direct-current Baliga's power figure of merit (PFOM) of 0.93 GW/cm2. In addition, we find that by shrinking the β-Ga2O3 width, the reverse leakage current is minimized due to the enhanced sidewall depletion effect from p-type NiOx. β-Ga2O3 HJBS diodes with p-type NiOx turn out to be an effective route for Ga2O3 power device technology by considering the high PFOM while maintaining a suppressed reverse leakage current.
Publisher: AIP Publishing
Date: 21-03-2022
DOI: 10.1063/5.0085367
Abstract: Epitaxial lateral overgrowth (ELO) is an effective strategy to achieve metastable phased α-Ga2O3 with low dislocation densities, which is desirable for developing ultralow-loss and ultrahigh power devices, whereas the involved dislocation dynamics have not been fully exploited. In this Letter, we investigated the dislocation propagations and reactions in α-Ga2O3 micropillar arrays selectively grown by halide vapor phase epitaxy technique. Screw dislocations in α-Ga2O3 micropillars grown from the selective area epitaxy (SAE) to ELO mode exhibited an independent character with an average density of 4.5 × 106 cm−2 while the edge dislocation density was reduced to 5.3 × 108 cm−2. During the initial SAE process, the α-Ga2O3 hexagonal pyramid is developed with the observed inversion domains within the pillar cores. The successive epitaxial lateral overgrowth ELO facilitates the formation of inclined facets upon the SiO2 mask. Almost complete filtering of the underlying threading dislocation has been demonstrated in the ELO wings. Strong image forces induced by inclined free surfaces drive the propagation and reaction of threading dislocations until annihilation, which is well described by the dislocation-filtering model during the dynamic geometry transition of micropillars. These findings may pave the way for the success of the heteroepitaxy of low dislocation density α-Ga2O3 toward the development of high-performance power devices.
Publisher: AIP Publishing
Date: 10-04-2023
DOI: 10.1063/5.0138426
Abstract: In this Letter, the trap inhomogeneity within β-Ga2O3 is correlated with the conversion of Shockley–Read–Hall (SRH) recombination in NiO/β-Ga2O3 p+–n heterojunction diodes. For the virgin epi-wafer, both near-surface traps E2 (EC-0.82 eV) and E3 (EC-1.11 eV) and bulk E2* traps (EC-0.76 eV) are identified by a transient capacitance analysis, and the corresponding forward current–voltage characteristics of diodes are well fitted in the framework of field-dependent SRH recombination. The SRH recombination rates for E2, E3, and E2* traps are determined to be 1.3 × 107, 8.6 × 108, and 2.4 × 108 s−1, respectively. In this circumstance, carrier transport under forward bias is governed by trap-assisted tunneling through E3 traps with high recombination rates, and the hysteresis is pronounced. With the removal of the defective surface layer, E2 and E3 traps are almost completely eliminated, together with the reduced density of E2* traps to 5.6 × 1014 cm−3. The resultant diode performs an improved rectification ratio of & at ±3 V and an enhanced reverse breakdown voltage of 1692 V. The elimination of near-surface traps leads to the conversion of carrier transport into the conventional SRH recombination, accompanied by the negligible forward hysteresis characteristics. The established fundamental correlation of carrier transport and traps within Ga2O3 is beneficial to develop a high-performance power rectifier toward practical applications.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2023
Publisher: AIP Publishing
Date: 27-12-2021
DOI: 10.1063/5.0071280
Abstract: In this Letter, we demonstrate a large-area (1-mm2) beveled-mesa p-NiO/β-Ga2O3 bipolar heterojunction diode (HJD) with a high Baliga's figure of merit of 1.84 (2.87) GW/cm2 from DC (pulsed) measurements. Benefiting from the suppression of electric field crowing at the designed mesa edge and bipolar current conductivity modulation, the resultant device exhibits advantageous characteristics, including a low subthreshold slope of 65 mV/decade, a low DC (pulsed) differential specific on-resistance of 2.26 (1.45) mΩ cm2, a high current density of 2 kA/cm2, and a high breakdown voltage of 2.04 kV. In particular, the Ga2O3 HJD exhibits an 800 V/10 A extreme switching capability with 16.4-ns reverse recovery characteristics, as well as high operation stability at a high temperature of 200 °C. This work, thus, makes a significant step toward reaching the promise of a high figure-of-merit in β-Ga2O3 power devices.
Publisher: IOP Publishing
Date: 17-01-2020
Publisher: American Chemical Society (ACS)
Date: 24-01-2019
Abstract: To suppress noise from full daylight background or environmental radiation, a spectrally selective solar-blind photodetector is widely required in many applications that need detection of light within a specific spectral range. Here, we present highly narrow-band solar-blind photodetectors by light polarization engineering of the anisotropic transitions in β-Ga
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2021
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 02-2022
Publisher: The Optical Society
Date: 07-03-2019
DOI: 10.1364/PRJ.7.000381
Publisher: AIP Publishing
Date: 03-07-2023
DOI: 10.1063/5.0147251
Abstract: We report an alignment-free gallium oxide (Ga2O3) heterojunction barrier Schottky (HJBS) power diode, which utilizes the self-assembled Ni nanostructures as in situ masks for the trench etching of Ga2O3 and the subsequent selective-area filling of p-type NiO. By increasing the trench depth to 200 nm, the relevant HJBS diode exhibits improved reverse blocking capabilities including the reduced leakage current density of 10−8 A/cm2 (at a reverse bias of 100 V) and the enhanced breakdown voltage of 748 V, while maintaining the forward biasing characteristics similar to the Schottky barrier diode (SBD). The variation of turn-on voltage and the reverse breakdown features indicate the conversion of the HJBS diodes characteristics from Ni/Ga2O3 SBD to the NiO/Ga2O3 p-n heterojunction diode. The electrical field simulations and experimental facts imply that the remarkable lateral pinch-off effect in the 200-nm trenched diodes shields the electric field in the depletion region underneath the Ni/Ga2O3 Schottky contact. This work provides a straightforward strategy to simplify the fabrication process of Ga2O3-based HJBS diodes with both promising forward and reverse performances.
Start Date: 07-2011
End Date: 07-2015
Amount: $245,538.00
Funder: Australian Research Council
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