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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
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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) - Dynamic drift effects in GaN power transistors: Correlation to device technology and mission profile
摘要： GaN devices for high voltage power switching are facilitating smaller, more light-weighted and more efficient converter systems. In order to provide an optimum design of such systems it is necessary to understand dynamic GaN device performance in dependence on targeted mission profile and technological parameters. The paper shortly introduces to GaN device technology and provides a widely accepted physical interpretation of mechanisms that may adversely influence device switching properties. Then important scenarios of GaN power transistor switching are presented and correlated to biasing conditions relevant for in-system device operation. In detail, dynamic switching properties depending on off- and on-state time and voltage, substrate biasing conditions and temperature are analysed and correlated to different device technologies and manufacturers. The abovementioned parameters are influencing dynamic device properties in quite a complex manner and can often be considered as a characteristic finger print of a specific technological implementation or a specific device or epitaxial manufacturer.
关键词： power switching,dynamic on-state resistance,drift effects,gallium nitride
更新于2025-09-09 09:28:46
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The Effect of Proton Irradiation in Suppressing Current Collapse in AlGaN/GaN High-Electron-Mobility Transistors
摘要： Almost complete suppression of dynamic ON-resistance in AlGaN/GaN high-electron-mobility transistors is obtained by proton irradiation. In this paper, both small and large power transistors are characterized before and after 3-MeV proton irradiation at different fluences. The irradiated devices show a high robustness and for specific fluences unaltered threshold voltage and static ON-resistance. However, for fluences higher than 1013 cm?2, the dynamic ON-resistance is almost completely suppressed at 600 V and T = 150 °C. After irradiation, a measurable increase in OFF-state leakage current is observed, indicating an increase in the unintentionally doped (UID) GaN layer conductivity. We propose a technology computer-aided design supported model in which this conductivity increase leads to an increased deionization rate, ultimately reducing the dynamic ON-resistance.
关键词： high-electron-mobility transistor (HEMT),proton irradiation,Gallium nitride (GaN),dynamic ON-resistance
更新于2025-09-09 09:28:46
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Chemical inactivity of GaN(0001) surface – The role of oxygen adsorption – Ab initio picture
摘要： Density Functional Theory (DFT) calculations were used to determine adsorption of oxygen at GaN(0001), i.e. Ga-terminated surface. It was shown that at low coverage the oxygen molecule dissociates during adsorption so that the two separate O adatoms are located in H3 sites. Oxygen adatom saturates three Ga broken bonds, modifying their energy by overlap with Op states, so that the three states are degenerate with valence band (VB). The electron counting rule (ECR) indicate on the electron surplus, the excess electrons are donated to other Ga broken bond states, the adsorption energy is equal to 3.74 eV/atom for clean surface. At the first critical coverage it is, the Fermi level is shifted to conduction band while at the second critical coverage shifted down to VBM. The adsorption energy is for, for and decreases and, respectively, for the energy jumps to, and for higher coverage the energy rapidly decreases to zero and becomes negative The singular point at is essential for stability of oxygen coverage of the surface. The equilibrium pressure at low coverage is 10?5 bar for 1500 K and 10?12 bar 1000 K. It is reduced for higher coverage, due to reduction of the energy and configurational entropy contributions. At the coverage the pressure is reduced by several orders of magnitude, indicating extremely high thermodynamic stability of such coverage, which is responsible for chemical inactivity of GaN(0001) surface observed in experiments, the critical factor for mechano-chemical polishing of the substrates for electronic applications.
关键词： Density functional theory,Surface,Oxygen,Gallium nitride
更新于2025-09-09 09:28:46
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High-performance spin rectification in gallium nitride-based molecular junctions with asymmetric edge passivation
摘要： The spin transport properties of molecular devices constructed from zigzag gallium nitride nanoribbons (ZGaNNRs) are investigated by applying the non-equilibrium Green’s function formalism in combination with density functional theory. The computational results indicate that ZGaNNR systems show spin rectification with a high efficiency, approaching nearly 109, giant magnetoresistance with a ratio up to 108, perfect spin-filtering, and negative differential resistance effects. Importantly, our results reveal that intrinsic rectification can be observed regardless of their width. The microscopic origins of the rectification are revealed and discussed in terms of a spin-resolved transmission spectrum, the band structures of the ZGaNNRs, and the molecular projected self-consistent Hamiltonian. Our findings could be useful for designing GaN-based spintronic nanodevices.
关键词： spin transport,molecular junctions,asymmetric edge passivation,gallium nitride,spintronic devices
更新于2025-09-09 09:28:46
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Electrical Performances of InN/GaN Tunneling Field-Effect Transistor
摘要： In this paper, we design and analyze the InN/GaN double-gate (DG) tunneling ?eld-effect transistor (TFET) with very steep switching and superb DC and RF characteristics. The proposed device is closely investigated in terms of both DC and RF performances including Ioff, on/off current ratio (Ion/Ioff), subthreshold swing (S), cut-off frequency (ft), maximum oscillating frequency (fmax), and Johnson’s ?gure of merit (JFOM) using TCAD simulation. The proposed InN/GaN TFET shows high current drivability, extremely suppressed Ioff, and higly sharp switching owing to the effects by the electron well formed by the control gate (CG) in the InN layer. The InN/GaN TFET having a channel length (Lch) of 50 nm demonstrated maximum Ion = 3.5 mA/μm, extremely low Ioff = 1 × 10?21 A/μm, minimum S of 8.8 mV/dec, and the maximum values of ft and fmax are obtained as 100 GHz and 5.5 THz, respectively. In order to con?rm the high performances of the devices in the RF operation, JFOM has been calculated and the value extracted from an optimally designed InN/GaN TFET is 1.7 THz · V.
关键词： III-Nitride Heterojunction,Double Gate,Gallium Nitride,Power Device,InN/GaN,Field-Effect Transistor
更新于2025-09-04 15:30:14
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Wafer-sized ultrathin gallium and indium nitride nanosheets through the ammonolysis of liquid metal derived oxides
摘要： We report the synthesis of centimeter sized ultrathin GaN and InN. The synthesis relies on the ammonolysis of liquid metal derived two-dimensional (2D) oxide sheets that were squeeze-transferred onto desired substrates. Wurtzite GaN nanosheets featured typical thicknesses of 1.3 nm, an optical bandgap of 3.5 eV and a carrier mobility of 21.5 cm2V-1s-1, while the InN featured a thickness of 2.0 nm. The deposited nanosheets were highly crystalline, grew along the (001) direction and featured a thickness of only three unit cells. The method provides a scalable approach for the integration of 2D morphologies of industrially important semiconductors into emerging electronics and optical devices.
关键词： ultrathin indium nitride,ultrathin gallium nitride,ammonolysis,two-dimensional materials,liquid metal derived oxides
更新于2025-09-04 15:30:14
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Modification of GaN thin film on sapphire substrate optical properties under weak magnetic fields
摘要： We present a study of the modifications to the optical transmittance of GaN thin film on sapphire substrate due to weak magnetic field (WMF) treatment. Measurements were performed in the 320-1100 nm wavelength range at 300 K, evidencing a change in transmission spectra for wavelengths above 700-800 nm after the WMF treatment. We use a model with three layers to simulate transmittance spectra. We have found that changes of the optical thickness induced by WMF are not sufficient to explain discrepancies between experimental and simulated spectra. To obtain a complete agreement it is necessary to consider a change in the refractive index of GaN and/or in the reflection coefficients for the interface air-GaN. We interpret such WMF-related effects as due to the diffusion of point defects after dissolution of metastable complexes from inner boundaries to surface of the structure. These defects modify optical properties of the GaN film.
关键词： reflectance,transmittance,weak magnetic field,gallium nitride
更新于2025-09-04 15:30:14
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Towards simulation at picometer-scale resolution: Revisiting inversion domain boundaries in GaN
摘要： Motivated by recent high resolution results on the inversion domain boundaries (IDB) in gallium nitride, we re?ne by ab initio DFT calculations the well established atomic model IDB? derived by Northrup et al. This allows us to recover these experimental results obtained by coherent x-ray diffraction and showing small additional shifts of the polarity domains, in particular 8 pm shift along the hexagonal direction. The in?uence of boundary conditions and electrostatic ?elds (IDB-IDB and IDB-surface interactions) on the results and the existence of metastable solutions is carefully discussed to stress the accuracy of the method. These results demonstrate a cross-talk between advanced characterization tools and state-of-the-art ab initio calculations that opens perspectives for the structural analysis of defects in the picometer range.
关键词： picometer resolution,ab initio DFT calculations,coherent x-ray diffraction,gallium nitride,inversion domain boundaries
更新于2025-09-04 15:30:14
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High germanium doping of GaN films by ammonia molecular beam epitaxy
摘要： Doping Gallium nitride (GaN) with elemental Germanium (Ge) grown by ammonia molecular beam epitaxy is presented. Growth studies varying the GaN growth rate, substrate growth temperature and the elemental Ge flux reveal several incorporation dependencies. Ge incorporation increases with flux, as expected, and a doping range from ~1017 cm-3 to 1020 cm-3 was readily achieved. A strong substrate temperature dependence on the electrical properties of films grown is observed, with an optimal growth temperature of 740 °C, lower than standard GaN growth conditions for the ammonia molecular beam epitaxy. Compensation effects at higher growth temperatures are suspected, as observed with other techniques. Crystallographic defects are apparent at the highest doping concentrations from electrical and optical measurements, however thin layers of such highly doped films are of great interest for contact layers and tunnel junctions in devices.
关键词： Ammonia Molecular Beam Epitaxy,Molecular Beam Epitaxy,Tunnel Junctions,Germanium Doping,Gallium Nitride
更新于2025-09-04 15:30:14