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The origin of carbon-related carrier compensation in p-type GaN layers grown by MOVPE
摘要： The role of carbon impurities in p-type GaN layers grown by metalorganic vapor phase epitaxy (MOVPE) was investigated. The lightly Mg-doped (～1017 cm?3) p-type GaN samples with different carbon concentration [C] were prepared by controlling growth temperature and pressure. Temperature-dependent Hall-effect analyses exhibited an increase in donor concentration with increasing [C]. The low-temperature mobility also decreased with increasing [C], as a result of mobility limitation due to ionized impurity scattering. These results show that carbon atoms in MOVPE-grown p-GaN layers act as ionized donors and cause carrier compensation. Deep-level transient spectroscopy (DLTS) using bias pulses detected the existence of Hd traps (EV +0.88 eV) arising from the 0/?1 charge state of carbon on nitrogen sites (CN). The concentrations of Hd traps closely corresponded to [C] values in p-type GaN layers. Employing low-frequency capacitance DLTS to avoid carrier freeze-out at low temperatures, we newly discovered the Ha trap (EV +0.29 eV) whose concentration was directly proportional to the [C] value. These ?ndings suggest that the Ha trap originates from CN identical to the Hd trap. Based on prior theoretical calculations of energy levels, the Ha trap can reasonably be assigned to a +1/0 donor state of CN. These results strongly suggest that a CN having two different charged states can compensate an electron and a hole in n-type and p-type GaN layers, respectively.
关键词： DLTS,p-type GaN,carrier compensation,MOVPE,carbon impurities
更新于2025-09-09 09:28:46
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Gan-Based Domain Adaptation for Object Classification
摘要： Recent trends in image classification focus on training deep neural networks that require having a large amount of training images related to the considered task. However, obtaining enough labeled image samples is often time-consuming and expensive. An alternative solution proposed is to transfer the knowledge learned while solving one problem to another but related problem, also called transfer learning. Domain adaptation is a type of transfer learning that deals with learning a model that performs well on two datasets that have different (but somehow correlated) data distributions. In this work, we present a new domain adaptation method based on generative adversarial networks (GANs) in the context of aerial image classification. Experimental results obtained on two datasets for a single object scenario show that the proposed method is particularly promising.
关键词： Deep learning,GAN,domain adaptation,transfer learning
更新于2025-09-09 09:28:46
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Light-Shield Layers Free Photosensitive Inverters Comprising GaN-Drivers and Multi-Layered MoS2-Loads
摘要： Herein, GaN driver FETs with a high energy bandgap are employed in photosensitive inverters to eliminate light-shield layers (LSLs). This configuration exhibits full-swing characteristics of photosensitive inverters comprised of multi-layered MoS2 FETs loads in photosensitive pseudo-depletion mode. The GaN FETs provide both high current drivability and excellent photo-leakage immunity under visible light (Eg~3.1 eV). This allows the photosensitive inverters to be successfully operational without LSLs. The relative degradation (%) of voltage gain for photosensitive inverters with GaN drivers from dark to blue light exposure is improved from 67.7% to 53.0 %, as compared to previously reported MoS2 inverters with LSLs.
关键词： light-shield layers (LSLs),GaN FETs,photosensitive inverters,MoS2 FETs,biosensors,low noise margin
更新于2025-09-09 09:28:46
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Rare Earth and Transition Metal Doping of Semiconductor Materials || Gadolinium-doped gallium-nitride
摘要： The race toward a dilute magnetic semiconductor (DMS) that exhibits room-temperature (RT) ferromagnetism has been in progress for about 15 years, sparked by the theoretical prediction that the two wide band-gap semiconductors GaN and ZnO would show a Curie temperature (TC) above 300 K if doped with 5% of Mn and a large hole concentration of 1 (cid:1) 1020/cm3 (Dietl et al., 2000). Despite apparent experimental evidence that RT magnetic order was already reported by many groups shortly after the theoretical prediction, the subject remained unusually controversial in the following years. Dietl (2010) summarizes that after 10 years of research the existence of ferromagnetism is well established for GaAs:Mn and related systems but it remains the major goal in the ?eld to achieve TCs at or above 300 K. Around the same time a review of a large group of theorists summarize: “The results of ab initio calculations seem to suggest that it is rather unlikely to obtain TC values as high as room temperature or above in this range” (Sato et al., 2010). Nonetheless persistent experimental claims of TCs above 300 K for a range of DMS materials can be found up to today. Thus it is worth trying to get a broader view on a given materials systems and compare a range of samples from different sources to elucidate whether these reports are characteristic of the DMS material itself (system-speci?c) or if only peculiarities of a given specimen are reported (sample-speci?c). Only in the former case can we consider those ?ndings to be useful for future potential applications in spintronic devices that have to be operational at ambient conditions.
关键词： ferromagnetism,room-temperature,GaN,Gd doping,dilute magnetic semiconductor
更新于2025-09-09 09:28:46
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Degradation of GaN-on-GaN vertical diodes submitted to high current stress
摘要： GaN-on-GaN vertical devices are expected to ?nd wide application in power electronics, thanks to the high current densities, the low on-resistance and the high breakdown voltage. So far, only few papers on the reliability of GaN-on-GaN vertical devices have been published in the literature. This paper investigates the degradation of GaN-on-GaN pn diodes submitted to stress at high current density. The study was carried out by means of electrical characterization and electroluminescence (EL) measurements. We demonstrate that: (i) when submitted to stress at high current density, the devices show signi?cant changes in the electrical characteristics: an increase in on-resistance/turn-on voltage, an increase in the generation/recombination components, the creation of shunt-paths. (ii) the increase in on-resistance is strongly correlated to the decrease in the EL signal emitted by the diodes. (iii) the degradation kinetics have a square-root dependence on time, indicative of a di?usion process. The results are interpreted by considering that stress induces a di?usion of hydrogen from the highly-p-type doped surface towards the pn junction. This results in a decrease in hole concentration, due to the creation of MgeH bonds, and in a lower hole injection. As a consequence, on-resistance increases while EL signal shows a correlated decrease.
关键词： Wide band gap semiconductors,Bulk GaN substrates,Vertical diodes,pn junction,Di?usion,Gallium nitride,Hydrogen,Degradation
更新于2025-09-09 09:28:46
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Light Emission by Nanoporous GaN Produced by a Top-Down, Nonlithographical Nanopatterning
摘要： Temperature-dependent photoluminescence (PL) spectroscopy is carried out to probe radiative recombination and related light emission processes in two-dimensional periodic close-packed nanopore arrays in gallium nitride (np-GaN). The arrays were produced by nonlithographic nanopatterning of wurtzite GaN followed by a dry etching. The results of Raman spectroscopy point to a small relaxation of the compressive stress of ~0.24 GPa in nanoporous vs. bulk GaN. At ~300 K, the PL emission is induced by excitons and not free-carrier interband radiative recombinations. An evolution of the emission spectra with T is con?rmed to be mainly a result of a decay of nonexcitonic PL emission and less of spectral shifts of the underlying PL bands. A switching of excitonic PL regime observed experimentally was analyzed within the exciton recombination-generation framework. The study provides new insights into the behaviors and physical mechanisms regulating light emission processes in np-GaN, critical to the development of nano-opto-electronic devices based on mesoscopic GaN.
关键词： photoluminescence,nonlithographic nanopatterning,Raman spectroscopy,nanoporous GaN,excitonic emission
更新于2025-09-09 09:28:46
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Trapping Effects Induced by Gate OFF-State Stress in AlGaN/GaN High-Electron-Mobility Transistors with Fe-Doped Buffer
摘要： This paper investigates the trapping characteristics in passivated Al0.23Ga0.77N/GaN High-Electron-Mobility transistors (HEMTs) with an Fe-doped buffer on Sapphire substrate. Double pulsed current–voltage (I–V ) measurements clearly exhibited the current collapse and slow detrapping transients characteristics. It is attributed to the injection of electron from gate to the traps located in the interface, the Al0.23Ga0.77N barrier and the Fe-doped buffer. By various pulse-widths of 0.5 μs, 5 μs, 10 μs, 50 μs and 0.1 ms and amplitudes of pulse-baseline (VGS-Q, VDS-Q) of ?6 V and ?8 V, we spatially analyzed the locations and corresponding detrapping time constants of the dominant traps in the device. Three different types of traps were found: a fast one with the time constant τ = 12–16 μs at the interface under gate, a middle one with τ = 0.12 ms in the AlGaN barrier layer, and a slow one in the Fe-doped GaN buffer under high reverse OFF-state stress with τ = 1.78 ms. Thus in the high voltage applications, the buffer-related deep traps are most significant.
关键词： Gate OFF-State Stress,Fe-Doped Buffer,Pulsed I–V,AlGaN/GaN HEMT,Trapping
更新于2025-09-09 09:28:46
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Systematic Investigation of Spontaneous Emission Quantum Efficiency Drop up to 800K for Future Power Electronics Applications
摘要： Future high-density power electronics applications may require optoelectronic devices for gate drive. Thus, a systematic study of optoelectronic material from 10 K to 800 K has been performed to understand the potential of the high-temperature operation of optoelectronic devices. The temperature dependence of the photoluminescence (PL) of InGaN/GaN multiple quantum wells (MWQs) was studied. The integrated PL intensity dropped by an order of magnitude at 800 K as compared to 10 K. The spontaneous emission quantum efficiency was calculated from the power-law relation linking the integrated PL signal and the excitation pump power. The validation of the traditional ABC model for solid-state lighting is extended to 800 K. This work demonstrates the feasibility of developing high-temperature optoelectronic devices, which have operating temperatures over 500 K.
关键词： high temperature photoluminescence,high temperature efficiency,power dependent photoluminescence,InGaN/GaN MWQs,power module,quantum temperature optoelectronics
更新于2025-09-09 09:28:46
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[IEEE 2018 International Power Electronics Conference (IPEC-Niigata 2018 –ECCE Asia) - Niigata, Japan (2018.5.20-2018.5.24)] 2018 International Power Electronics Conference (IPEC-Niigata 2018 -ECCE Asia) - A Study on Load Fluctuation of Isolated DC-DC Converter with Class Phi-2 Inverter using GaN-HFET
摘要： In recent years, the development and application of GaN-HFET(Heterojunction Field Effect Transistor) has become actively. As GaN-HFETs have advantages in high frequency operation, it is possible to down size power converters by rising switching frequency. In this paper, we investigate the load fluctuation of an isolated DC-DC converter with the class Phi-2 inverter circuit using GaN-HEFT, which is operated at 13.56 MHz.
关键词： DC-DC Converter,Resonant Converter,GaN-HFET,WBG Semiconductor
更新于2025-09-09 09:28:46
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[IEEE 2018 International Power Electronics Conference (IPEC-Niigata 2018 –ECCE Asia) - Niigata, Japan (2018.5.20-2018.5.24)] 2018 International Power Electronics Conference (IPEC-Niigata 2018 -ECCE Asia) - Design of a High-Frequency Dual-Active Bridge Converter with GaN Devices for an Output Power of 3.7 kW
摘要： In the automotive industry weight and volume are important issues to design power electronics besides costs. With the upcoming of wide band-gap devices like Gallium Nitride (GaN) devices high switching frequencies become a potential for converters. Operating at high switching frequencies reduces the volume of passive components e.g., transformer significantly. Auxiliary supplies or on-board charging systems for electric vehicles are typical areas of application for a reduction of volume and weight. For this kind of application dc-dc converters like a Dual Active Bridge converter can be used. This paper describes a detailed electrical analysis of a compact single phase Dual Active Bridge converter operated at a high switching frequency of 500 kHz at a dc voltage of 400 V on both full bridges to achieve a power transfer of 3.7 kW. In this paper it is shown how a fast switching and compact dual active bridge converter is designed that operates with a high efficiency of about 96% at nominal power.
关键词： Gallium Nitride (GaN) devices,Dual Active Bridge converter,electric vehicles,power electronics,high switching frequencies
更新于2025-09-09 09:28:46