High electron mobility transistor(HEMT)based on gallium nitride(GaN)is one of the most promising candidates for the future generation of high frequencies and high-power electronic applications.This research work aims ...High electron mobility transistor(HEMT)based on gallium nitride(GaN)is one of the most promising candidates for the future generation of high frequencies and high-power electronic applications.This research work aims at designing and characterization of enhancement-mode or normally-off GaN HEMT.The impact of variations in gate length,mole concentration,barrier variations and other important design parameters on the performance of normally-off GaN HEMT is thoroughly investigated.An increase in the gate length causes a decrease in the drain current and transconductance,while an increase in drain current and transconductance can be achieved by increasing the concentration of aluminium(Al).For Al mole fractions of 23%,25%,and 27%,within Al gallium nitride(AlGaN)barrier,the GaN HEMT devices provide a maximum drain current of 347,408 and 474 mA/μm and a transconductance of 19,20.2,21.5 mS/μm,respectively.Whereas,for Al mole fraction of 10%and 15%,within AlGaN buffer,these devices are observed to provide a drain current of 329 and 283 mA/μm,respectively.Furthermore,for a gate length of 2.4,3.4,and 4.4μm,the device is observed to exhibit a maximum drain current of 272,235,and 221 mA/μm and the transconductance of 16.2,14,and 12.3 mS/μm,respectively.It is established that a maximum drain current of 997 mA/μm can be achieved with an Al concentration of 23%,and the device exhibits a steady drain current with enhanced transconductance.These observations demonstrate tremendous potential for two-dimensional electron gas(2DEG)for securing of the normally-off mode operation.A suitable setting of gate length and other design parameters is critical in preserving the normally-off mode operation while also enhancing the critical performance parameters at the same time.Due to the normallyon depletion-mode nature of GaN HEMT,it is usually not considered as suitable for high power levels,frequencies,and temperature.In such settings,a negative bias is required to enter the blocking condition;however,in the before-mentioned normally-off devices,the negative bias can be avoided and the channel can be depleted without applying a negative bias.展开更多
Gallium nitride(GaN)/porous silicon(PSi)film was prepared using a pulsed laser deposition method and 1064 nm Nd:YAG laser for optoelectronic applications and a series of Psi substrates were fabricated using a photoele...Gallium nitride(GaN)/porous silicon(PSi)film was prepared using a pulsed laser deposition method and 1064 nm Nd:YAG laser for optoelectronic applications and a series of Psi substrates were fabricated using a photoelectrochemical etching method assisted by laser at different etching times for 2.5–15 min at 2.5 min intervals.X-ray diffraction,room-temperature photoluminescence,atomic force microscopy and field emission scanning electron microscopy images,and electrical characteristics in the prepared GaN on the Psi film were investigated.The optimum Psi substrate was obtained under the following conditions:10 min,10 mA/cm^(2),and 24%hydrofluoric acid.The substrate exhibited two highly cubic crystalline structures at(200)and(400)orientations and yellow visible band photoluminescence,and homogeneous pores formed over the entire surface.The pores had steep oval shapes and were accompanied by small dark pores that appeared topographically and morphologically.The GaN/Psi film fabricated through PLD exhibited a high and hexagonal crystallographic texture in the(002)plane.Spectroscopic properties results revealed that the photoluminescence emission of the deposited nano-GaN films was in the ultraviolet band(374 nm)related to GaN material and in the near-infrared band(730 nm)related to the Psi substrate.The topographical and morphological results of the GaN films confirmed that the deposited film contained spherical grains with an average diameter of 51.8 nm and surface roughness of 4.8 nm.The GaN/Psi surface showed a cauliflower-like morphology,and the built-in voltage decreased from 3.4 to 2.7 eV after deposition.The fabricated GaN/Psi film exhibited good electrical characteristics.展开更多
With technology computer-aided design(TCAD)simulation software,we design a new structure of gallium oxide on gallium-nitride Schottky barrier diode(SBD).The parameters of gallium oxide are defined as new material para...With technology computer-aided design(TCAD)simulation software,we design a new structure of gallium oxide on gallium-nitride Schottky barrier diode(SBD).The parameters of gallium oxide are defined as new material parameters in the material library,and the SBD turn-on and breakdown behavior are simulated.The simulation results reveal that this new structure has a larger turn-on current than Ga2O3 SBD and a larger breakdown voltage than Ga N SBD.Also,to solve the lattice mismatch problem in the real epitaxy,we add a Zn O layer as a transition layer.The simulations show that the device still has good properties after adding this layer.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
采用点缺陷线性分布模型,利用能量弛豫方法得到了基于van der Pauw变温霍尔效应测量来确定纤锌矿n-GaN位错密度的新方法.用高分辨率X射线衍射仪测试了两个分别用MOCVD方法和用HVPE方法生长的n-GaN样品,用Srikant方法拟合得到了位错密度...采用点缺陷线性分布模型,利用能量弛豫方法得到了基于van der Pauw变温霍尔效应测量来确定纤锌矿n-GaN位错密度的新方法.用高分辨率X射线衍射仪测试了两个分别用MOCVD方法和用HVPE方法生长的n-GaN样品,用Srikant方法拟合得到了位错密度.结果表明两种方法高度一致.进一步的研究表明,新方法和化学腐蚀方法的测试结果基本一致,相关拟合参数与采用Rode迭代法精确求解Boltzmann输运方程的理论结果也基本一致.研究还表明,新方法能有效消除施主杂质带和界面简并层对测试结果的影响,测试剔除界面层影响后的整个外延层的刃、螺位错密度,而不是穿透位错密度.该方法适合霍尔迁移率曲线峰位在200 K左右及以下并且峰位明确的各种生长工艺、各种厚度、各种质量层次的薄膜和体材料,具有对迁移率曲线高度拟合,材料参数精确,计算简便、收敛速度快等优点.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。
文摘High electron mobility transistor(HEMT)based on gallium nitride(GaN)is one of the most promising candidates for the future generation of high frequencies and high-power electronic applications.This research work aims at designing and characterization of enhancement-mode or normally-off GaN HEMT.The impact of variations in gate length,mole concentration,barrier variations and other important design parameters on the performance of normally-off GaN HEMT is thoroughly investigated.An increase in the gate length causes a decrease in the drain current and transconductance,while an increase in drain current and transconductance can be achieved by increasing the concentration of aluminium(Al).For Al mole fractions of 23%,25%,and 27%,within Al gallium nitride(AlGaN)barrier,the GaN HEMT devices provide a maximum drain current of 347,408 and 474 mA/μm and a transconductance of 19,20.2,21.5 mS/μm,respectively.Whereas,for Al mole fraction of 10%and 15%,within AlGaN buffer,these devices are observed to provide a drain current of 329 and 283 mA/μm,respectively.Furthermore,for a gate length of 2.4,3.4,and 4.4μm,the device is observed to exhibit a maximum drain current of 272,235,and 221 mA/μm and the transconductance of 16.2,14,and 12.3 mS/μm,respectively.It is established that a maximum drain current of 997 mA/μm can be achieved with an Al concentration of 23%,and the device exhibits a steady drain current with enhanced transconductance.These observations demonstrate tremendous potential for two-dimensional electron gas(2DEG)for securing of the normally-off mode operation.A suitable setting of gate length and other design parameters is critical in preserving the normally-off mode operation while also enhancing the critical performance parameters at the same time.Due to the normallyon depletion-mode nature of GaN HEMT,it is usually not considered as suitable for high power levels,frequencies,and temperature.In such settings,a negative bias is required to enter the blocking condition;however,in the before-mentioned normally-off devices,the negative bias can be avoided and the channel can be depleted without applying a negative bias.
文摘Gallium nitride(GaN)/porous silicon(PSi)film was prepared using a pulsed laser deposition method and 1064 nm Nd:YAG laser for optoelectronic applications and a series of Psi substrates were fabricated using a photoelectrochemical etching method assisted by laser at different etching times for 2.5–15 min at 2.5 min intervals.X-ray diffraction,room-temperature photoluminescence,atomic force microscopy and field emission scanning electron microscopy images,and electrical characteristics in the prepared GaN on the Psi film were investigated.The optimum Psi substrate was obtained under the following conditions:10 min,10 mA/cm^(2),and 24%hydrofluoric acid.The substrate exhibited two highly cubic crystalline structures at(200)and(400)orientations and yellow visible band photoluminescence,and homogeneous pores formed over the entire surface.The pores had steep oval shapes and were accompanied by small dark pores that appeared topographically and morphologically.The GaN/Psi film fabricated through PLD exhibited a high and hexagonal crystallographic texture in the(002)plane.Spectroscopic properties results revealed that the photoluminescence emission of the deposited nano-GaN films was in the ultraviolet band(374 nm)related to GaN material and in the near-infrared band(730 nm)related to the Psi substrate.The topographical and morphological results of the GaN films confirmed that the deposited film contained spherical grains with an average diameter of 51.8 nm and surface roughness of 4.8 nm.The GaN/Psi surface showed a cauliflower-like morphology,and the built-in voltage decreased from 3.4 to 2.7 eV after deposition.The fabricated GaN/Psi film exhibited good electrical characteristics.
文摘With technology computer-aided design(TCAD)simulation software,we design a new structure of gallium oxide on gallium-nitride Schottky barrier diode(SBD).The parameters of gallium oxide are defined as new material parameters in the material library,and the SBD turn-on and breakdown behavior are simulated.The simulation results reveal that this new structure has a larger turn-on current than Ga2O3 SBD and a larger breakdown voltage than Ga N SBD.Also,to solve the lattice mismatch problem in the real epitaxy,we add a Zn O layer as a transition layer.The simulations show that the device still has good properties after adding this layer.
文摘采用点缺陷线性分布模型,利用能量弛豫方法得到了基于van der Pauw变温霍尔效应测量来确定纤锌矿n-GaN位错密度的新方法.用高分辨率X射线衍射仪测试了两个分别用MOCVD方法和用HVPE方法生长的n-GaN样品,用Srikant方法拟合得到了位错密度.结果表明两种方法高度一致.进一步的研究表明,新方法和化学腐蚀方法的测试结果基本一致,相关拟合参数与采用Rode迭代法精确求解Boltzmann输运方程的理论结果也基本一致.研究还表明,新方法能有效消除施主杂质带和界面简并层对测试结果的影响,测试剔除界面层影响后的整个外延层的刃、螺位错密度,而不是穿透位错密度.该方法适合霍尔迁移率曲线峰位在200 K左右及以下并且峰位明确的各种生长工艺、各种厚度、各种质量层次的薄膜和体材料,具有对迁移率曲线高度拟合,材料参数精确,计算简便、收敛速度快等优点.
