Elucidating the complex interactions between the work material and abrasives during grinding of gallium nitride(GaN)single crystals is an active and challenging research area.In this study,molecular dynamics simulatio...Elucidating the complex interactions between the work material and abrasives during grinding of gallium nitride(GaN)single crystals is an active and challenging research area.In this study,molecular dynamics simulations were performed on double-grits interacted grinding of GaN crystals;and the grinding force,coefficient of friction,stress distribution,plastic damage behaviors,and abrasive damage were systematically investigated.The results demonstrated that the interacted distance in both radial and transverse directions achieved better grinding quality than that in only one direction.The grinding force,grinding induced stress,subsurface damage depth,and abrasive wear increase as the transverse interacted distance increases.However,there was no clear correlation between the interaction distance and the number of atoms in the phase transition and dislocation length.Appropriate interacted distances between abrasives can decrease grinding force,coefficient of friction,grinding induced stress,subsurface damage depth,and abrasive wear during the grinding process.The results of grinding tests combined with cross-sectional transmission electron micrographs validated the simulated damage results,i.e.amorphous atoms,high-pressure phase transition,dislocations,stacking faults,and lattice distortions.The results of this study will deepen our understanding of damage accumulation and material removal resulting from coupling between abrasives during grinding and can be used to develop a feasible approach to the wheel design of ordered abrasives.展开更多
It remains a big challenge to synthesize two-dimensional(2D)GaN material for applications in power nanodevices.Traditional synthetic methods require complex equipment and processes and time consuming.Here,we reported ...It remains a big challenge to synthesize two-dimensional(2D)GaN material for applications in power nanodevices.Traditional synthetic methods require complex equipment and processes and time consuming.Here,we reported a two-step route to prepare polycrystalline 2D GaN film.The amorphous ultrathin Ga_(2)O_(3)film was first exfoliated from the surface of liquid gallium.In a vapor phase reaction,2D Ga_(2)O_(3)film was then converted into 2D GaN film while maintaining the 2D morphology.Raman and high-resolution transmission electron microscope(HRTEM)analysis implies the successful synthesis of wurtzite-type GaN ultrathin film.This simple strategy proposed in this work will provide more opportunities for applications of GaN ultrathin film in many devices.展开更多
为了实现对氮化镓高电子迁移率晶体管GaN HEMT(gallium nitride high electron mobility transistor)高速开关带来的开通过压、误导通、开关振荡和EMI噪声等问题展开定量的仿真分析,提出了一种基于建模数据和最优化算法的门极增强型GaN ...为了实现对氮化镓高电子迁移率晶体管GaN HEMT(gallium nitride high electron mobility transistor)高速开关带来的开通过压、误导通、开关振荡和EMI噪声等问题展开定量的仿真分析,提出了一种基于建模数据和最优化算法的门极增强型GaN HEMT电热行为模型建模方法。相比较于常规GaN HEMT行为模型,所提出的建模方法采用2个简单的建模公式实现了对GaN HEMT在第一和第三象限宽工作温度范围内的电热特性进行准确的建模。同时采用一个紧凑的建模公式实现对GaN HEMT非线性寄生电容的精确建模。此外,提出了一种遗传算法和Levenberg-Marquardt算法组合的优化算法,基于该优化算法和建模数据实现了对建模参数的快速提取,在较大程度上减小了建模时间和工作量。仿真表明,所提出的建模方法能够实现对不同公司多个型号的GaN HEMT器件展开精确的建模。最后通过吻合的动态仿真和实验数据验证了所提建模方法的正确性和有效性。展开更多
增强型氮化镓(GaN)基高电子迁移率晶体管(high electron mobility transistor,HEMT)是高频高功率器件与开关器件领域的研究热点,P-GaN栅技术因具备制备工艺简单、可控且工艺重复性好等优势而成为目前最常用且唯一实现商用的GaN基增强型...增强型氮化镓(GaN)基高电子迁移率晶体管(high electron mobility transistor,HEMT)是高频高功率器件与开关器件领域的研究热点,P-GaN栅技术因具备制备工艺简单、可控且工艺重复性好等优势而成为目前最常用且唯一实现商用的GaN基增强型器件制备方法。首先,概述了当前制约P-GaN栅结构GaN基HEMT器件发展的首要问题,从器件结构与器件制备工艺这2个角度,综述了其性能优化举措方面的最新研究进展。然后,通过对研究进展的分析,总结了当前研究工作面临的挑战以及解决方法。最后,对未来的发展前景、发展方向进行了展望。展开更多
Due to the remarkable growth rate compared to another growth methods for gallium nitride(GaN)growth,hydride vapor phase epitaxy(HVPE)is now the only method for mass product GaN substrates.In this review,commercial HVP...Due to the remarkable growth rate compared to another growth methods for gallium nitride(GaN)growth,hydride vapor phase epitaxy(HVPE)is now the only method for mass product GaN substrates.In this review,commercial HVPE systems and the GaN crystals grown by them are demonstrated.This article also illustrates some innovative attempts to develop homebuilt HVPE systems.Finally,the prospects for the further development of HVPE for GaN crystal growth in the future are also discussed.展开更多
For thermally stable or high-temperature operating,Schottky contact utilizing refractory metal nitride,TiN,MoN and ZrN,on n-GaN were evaluated.The refractory metal nitride films were formed by reactive sputtering in A...For thermally stable or high-temperature operating,Schottky contact utilizing refractory metal nitride,TiN,MoN and ZrN,on n-GaN were evaluated.The refractory metal nitride films were formed by reactive sputtering in Ar and N2 ambient.Current-voltage characteristics show that ideality factors of 1.09-1.22 and barrier heights of 0.66-0.75 eV was obtained for the three metal nitrides.For the ZrN contact,the ideality factor and barrier height of became 1.06 and 0.77 eV,respectively,after 800 ℃ annealing.AlGaN/GaN heterostructure FET with TiN gate was also investigated.No obvious degradation was found for the TiN-gate device even after thermal treatment at 850 ℃.This shows that Schottky contact utilizing refractory metal nitride on GaN has the potential for thermal stability or high-temperature operating.展开更多
Graphene on gallium nitride （GaN） will be quite useful when the graphene is used as transparent electrodes to improve the performance of gallium nitride devices. In this work, we report the direct synthesis of graph...Graphene on gallium nitride （GaN） will be quite useful when the graphene is used as transparent electrodes to improve the performance of gallium nitride devices. In this work, we report the direct synthesis of graphene on GaN without an extra catalyst by chemical vapor deposition. Raman spectra indicate that the graphene films are uniform and about 5-6 layers in thickness. Meanwhile, the effects of growth temperatures on the growth of graphene films are systematically studied, of which 950 ℃ is found to be the optimum growth temperature. The sheet resistance of the grown graphene is 41.1 Ω/square, which is close to the lowest sheet resistance of transferred graphene reported. The mechanism of graphene growth on GaN is proposed and discussed in detail. XRD spectra and photoluminescence spectra indicate that the quality of GaN epi-layers will not be affected after the growth of graphene.展开更多
文摘采用金属有机物化学气相沉积(Metal organic chemical vapor deposition,MOCVD)技术在101.6 mm(4英寸)半绝缘SiC衬底上开展太赫兹用GaN肖特基势垒二极管(Schottky barrier diode,SBD)外延材料应力演进及缺陷密度控制的研究。提出了一种基于AlGaN过渡层的应力调控方案,实现了外延材料的应力调控;采用低温脉冲式掺杂技术生长n+-GaN层,降低了外延材料的缺陷密度,提升了晶体质量。研制的101.6 mm GaN SBD外延材料的弯曲度(Bow)/翘曲度(Warp)为-12/18μm,(002)/(102)面半高宽为148/239 arcsec,方阻9.2Ω/□,方阻片内不均匀性1.1%,并基于自研材料实现了截止频率为1.12 THz的GaN SBD器件的研制。
基金supported by the National Natural Science Foundation of China(52375420,52005134 and51675453)Natural Science Foundation of Heilongjiang Province of China(YQ2023E014)+5 种基金Self-Planned Task(No.SKLRS202214B)of State Key Laboratory of Robotics and System(HIT)China Postdoctoral Science Foundation(2022T150163)Young Elite Scientists Sponsorship Program by CAST(No.YESS20220463)State Key Laboratory of Robotics and System(HIT)(SKLRS-2022-ZM-14)Open Fund of Key Laboratory of Microsystems and Microstructures Manufacturing(HIT)(2022KM004)Fundamental Research Funds for the Central Universities(Grant Nos.HIT.OCEF.2022024 and FRFCU5710051122)。
文摘Elucidating the complex interactions between the work material and abrasives during grinding of gallium nitride(GaN)single crystals is an active and challenging research area.In this study,molecular dynamics simulations were performed on double-grits interacted grinding of GaN crystals;and the grinding force,coefficient of friction,stress distribution,plastic damage behaviors,and abrasive damage were systematically investigated.The results demonstrated that the interacted distance in both radial and transverse directions achieved better grinding quality than that in only one direction.The grinding force,grinding induced stress,subsurface damage depth,and abrasive wear increase as the transverse interacted distance increases.However,there was no clear correlation between the interaction distance and the number of atoms in the phase transition and dislocation length.Appropriate interacted distances between abrasives can decrease grinding force,coefficient of friction,grinding induced stress,subsurface damage depth,and abrasive wear during the grinding process.The results of grinding tests combined with cross-sectional transmission electron micrographs validated the simulated damage results,i.e.amorphous atoms,high-pressure phase transition,dislocations,stacking faults,and lattice distortions.The results of this study will deepen our understanding of damage accumulation and material removal resulting from coupling between abrasives during grinding and can be used to develop a feasible approach to the wheel design of ordered abrasives.
基金Funded by the National Natural Science Foundation of China(No.52172124)the Fundamental Research Funds for the Central Universities(WUT:2021III019JC)。
文摘It remains a big challenge to synthesize two-dimensional(2D)GaN material for applications in power nanodevices.Traditional synthetic methods require complex equipment and processes and time consuming.Here,we reported a two-step route to prepare polycrystalline 2D GaN film.The amorphous ultrathin Ga_(2)O_(3)film was first exfoliated from the surface of liquid gallium.In a vapor phase reaction,2D Ga_(2)O_(3)film was then converted into 2D GaN film while maintaining the 2D morphology.Raman and high-resolution transmission electron microscope(HRTEM)analysis implies the successful synthesis of wurtzite-type GaN ultrathin film.This simple strategy proposed in this work will provide more opportunities for applications of GaN ultrathin film in many devices.
文摘增强型氮化镓(GaN)基高电子迁移率晶体管(high electron mobility transistor,HEMT)是高频高功率器件与开关器件领域的研究热点,P-GaN栅技术因具备制备工艺简单、可控且工艺重复性好等优势而成为目前最常用且唯一实现商用的GaN基增强型器件制备方法。首先,概述了当前制约P-GaN栅结构GaN基HEMT器件发展的首要问题,从器件结构与器件制备工艺这2个角度,综述了其性能优化举措方面的最新研究进展。然后,通过对研究进展的分析,总结了当前研究工作面临的挑战以及解决方法。最后,对未来的发展前景、发展方向进行了展望。
基金supported by the National Key Research and Development Plan (No. 2017YFB0404201)the National Science Foundation of China (Nos. 61774147, 61874108)
文摘Due to the remarkable growth rate compared to another growth methods for gallium nitride(GaN)growth,hydride vapor phase epitaxy(HVPE)is now the only method for mass product GaN substrates.In this review,commercial HVPE systems and the GaN crystals grown by them are demonstrated.This article also illustrates some innovative attempts to develop homebuilt HVPE systems.Finally,the prospects for the further development of HVPE for GaN crystal growth in the future are also discussed.
文摘For thermally stable or high-temperature operating,Schottky contact utilizing refractory metal nitride,TiN,MoN and ZrN,on n-GaN were evaluated.The refractory metal nitride films were formed by reactive sputtering in Ar and N2 ambient.Current-voltage characteristics show that ideality factors of 1.09-1.22 and barrier heights of 0.66-0.75 eV was obtained for the three metal nitrides.For the ZrN contact,the ideality factor and barrier height of became 1.06 and 0.77 eV,respectively,after 800 ℃ annealing.AlGaN/GaN heterostructure FET with TiN gate was also investigated.No obvious degradation was found for the TiN-gate device even after thermal treatment at 850 ℃.This shows that Schottky contact utilizing refractory metal nitride on GaN has the potential for thermal stability or high-temperature operating.
基金supported by the National Natural Science Foundation of China(Grant Nos.61274040 and 51102226)the National Basic Research Program of China(Grant No.2011CB301904)+2 种基金the National High Technology Program of China(Grant Nos.2011AA03A103 and 2011AA03A105)the National Science Foundation of China(Grant Nos.10774032 and 90921001)the Key Knowledge Innovation Project of the Chinese Academy of Sciences on Water Science Research,Instrument Developing Project of the Chinese Academy of Sciences(Grant No.Y2010031)
文摘Graphene on gallium nitride （GaN） will be quite useful when the graphene is used as transparent electrodes to improve the performance of gallium nitride devices. In this work, we report the direct synthesis of graphene on GaN without an extra catalyst by chemical vapor deposition. Raman spectra indicate that the graphene films are uniform and about 5-6 layers in thickness. Meanwhile, the effects of growth temperatures on the growth of graphene films are systematically studied, of which 950 ℃ is found to be the optimum growth temperature. The sheet resistance of the grown graphene is 41.1 Ω/square, which is close to the lowest sheet resistance of transferred graphene reported. The mechanism of graphene growth on GaN is proposed and discussed in detail. XRD spectra and photoluminescence spectra indicate that the quality of GaN epi-layers will not be affected after the growth of graphene.
