AlGaN/GaN HEMT二维静态模型与模拟

考虑AlGaN/GaN材料的自发、压电极化效应和量子效应,通过泊松方程、薛定谔方程和流体力学方程组的数值自洽求解方法,对AlGaN/GaN HEMT的二维静态模型与模拟问题进行了研究,得到了器件区域的导带图、二维电子气分布、电子温度特性、直流输出和转移特性,并对模拟结果进行了分析与讨论.     

AlGaN/GaN材料HEMT器件优化分析与I-V特性

在考虑AlGaN/GaN异质结中的压电极化和自发极化效应的基础上,自洽求解了垂直于沟道方向的薛定谔方程和泊松方程.通过模拟计算,研究了AlGaN/GaN HEMT器件掺杂层Al的组分、厚度、施主掺杂浓度以及栅偏压对二维电子气特性的影响.用准二维物理模型计算了AlGaN/GaN HEMT器件的输出特性,给出了相应的饱和电压和阈值电压,并对计算结果和AlGaN/GaN HEMT器件的结构优化进行了分析.     

RF-MBE生长AlGaN/GaN极化感应二维电子气材料

用射频等离子体辅助分子束外延技术(RF-MBE)在C面蓝宝石衬底上外延了高质量的GaN膜以及AlGaN/GaN极化感应二维电子气材料.所外延的GaN膜室温背景电子浓度为2×1017cm-a,相应的电子迁移率为177cm2/(V·s);GaN(0002)X射线衍射摇摆曲线半高宽(FWHM)为6′;AlGaN/GaN极化感应二维电子气材料的室温电子迁移率为730cm2/(V·s),相应的电子气面密度为7.6×1012cm-2;用此二维电子气材料制作的异质结场效应晶体管(HFET)室温跨导达50mS/mm(栅长1μm),截止频率达13GHz(栅长0.5μm).     

AlN阻挡层对AlGaN/GaNHEMT器件的影响

利用低压MOCVD技术在蓝宝石衬底上生长了AlGaN/GaN异质结和AlGaN/AlN/GaN异质结二维电子气材料,采用相同器件工艺制造出了AlGaN/GaN HEMT器件和AlGaN/AlN/GaN HEMT器件.通过对两种不同器件的比较和讨论,研究了AlN阻挡层的增加对AlGaN/GaN HEMT器件性能的影响.     

AlN阻挡层对AlGaN/GaN HEMT器件的影响

利用低压MOCVD技术在蓝宝石衬底上生长了AlGaN/GaN异质结和AlGaN/AlN/GaN异质结二维电子气材料,采用相同器件工艺制造出了AlGaN/GaN HEMT器件和AlGaN/AlN/GaN HEMT器件.通过对两种不同器件的比较和讨论,研究了AlN阻挡层的增加对AlGaN/GaN HEMT器件性能的影响.     

AlGaN／GaN二维电子气的特性研究

应用AlGaN/GaN异质结中的压电极化和自发极化边界条件自洽求解了薛定谔方程和泊松方程,求出异质结能带和二维电子气分布。研究了势垒层组分化、势垒层宽度、沟道层掺杂和栅电压变化对二维电子气特性的影响。着重研究了栅电压对二维电子气维性的控制作用,提出了使用薄势垒和重掺杂沟道的新HFET结构。     

AlGaN/GaN HEMT电容及充电时间的研究

通过计算AlGaN/GaN HEMT二维电子气中的电势、载流子以及调制掺杂载流子寿命,得到AlGaN/GaN HEMT电容和充电时间,研究了AlGaN掺杂层浓度和厚度对器件的时间响应分析了AlGaN/GaN HEMT器件的高频特性。结果表明,栅电容随着AlGaN掺杂层浓度和厚度的增加逐渐减小。随着AlGaN层掺杂浓度的增大,电容充电时间先减后增,当掺杂浓度达到 时,电容充电时间达到极小值,在AlGaN掺杂层厚度等于7nm时电容充电时间最短。     

AlGaN/GaN基HEMT器件的研究进展(英文)

由于AlGaN具有高的击穿电场(3 MV/cm,是GaAs的7.5倍),且在AlGaN/GaN异质结处存在高浓度的极化诱导二维电子气,AlGaN基高电子迁移率晶体管是目前最适合应用于微波大功率放大领域的器件。着重对影响高频大功率AlGaN/GaN性能的材料结构和器件制作进行了阐述。     

表面态对AlGaN/GaN异质结构中二维电子气的影响

基于静电学分析,得出表面态是电子的一个重要来源.基于这一分析,可以解释已发表的关于二维电子气(2DEC)的大量数据.例如,2DEG密度随着AlGaN层厚度、Al组分的变化的原因.当A10.3Ga0.7N/GaN结构中生长一层5 nm厚的GaN冒层时,2DEG浓度由1.47×1013cm-2减少到1.20×1013cm-2,减少是由于表面类施主态离化减少.由于充分厚的GaN冒层导致GaN/AlGaN/GaN上界面形成二维空穴气(2DHG),所以在超出特定的冒层厚度时2DEG浓度达到饱和.     

AlGaN/GaN/AlGaN双异质结材料生长及性质研究

基于能带理论设计并利用MOCVD技术在76.2 mm蓝宝石衬底上生长了不同GaN沟道层厚度的AlGaN/GaN/AlGaN双异质结材料.室温霍尔测试结果表明:双异质结材料的二维电子气面密度随沟道层厚度增加有所升高并趋于饱和;二维电子气迁移率则随沟道厚度增加明显升高.200 nm厚GaN沟道的双异质结材料方块电阻平均值3...     

Analytical modelling and electrical characterisation of ZnO based HEMTs

Conventionally, Poisson’s equation coupled with 1-D Schrödinger’s equation is solved self-consistently in the triangular quantum well to calculate 2DEG density at the heterointerface. 2DEG density hence derived is a complicated transcendental function which cannot be solved analytically. Therefore, in this work, we use a simple expression for Fermi energy level to develop a compact physics-based 2D-analytical model for 2DEG density. The calculated 2DEG density from this model is validated with earlier reported experimental results. Using this 2DEG density, an expression for I-V characteristics of HEMTs has also been developed. The I-V characteristics of a buffer layer engineered MgZnO/CdZnO HEMT for improved 2DEG density have been analysed for the first time using developed model to the best of our knowledge.     

AlGaN/GaN HFET的2DEG和电流崩塌研究(Ⅰ)

从不同的视角回顾和研究了A1GaN/GaN HFET的二维电子气(2DEG)和电流崩塌问题.阐述了非掺杂的AIGaN/GaN异质结界面存在2DEG的原动力是极化效应,电子来源是AlGaN上的施主表面态.2DEG浓度与AlGaN/GaN界面导带不连续性、AlGaN层厚和Al组分有密切关系.揭示了AlGaN/GaN HFET的2DEG电荷涨落受控于表面、界面和缓冲层中的各种缺陷及外加应力,表面空穴陷阱形成的虚栅对输入信号有旁路和延迟作用,它们导致高频及微波状态下的电流崩塌.指出由于构成电流崩塌因素的复杂性,各种不同的抑制电流崩塌方法都存在不足,因此实现该器件大功率密度和高可靠性还有很长的路要走.     

在外磁场作用下Rashba系统中的磁光吸收谱

基于半经典玻尔兹曼方程的方法研究了InGaAs/InAlAs 系统中电子在Rashba自旋轨道耦合相互作用(RSOI)和外磁场作用下二维电子气(2DEG)的磁光吸收谱以及选择定则。RSOI的存在使朗道能级相互混合并移动, 在高迁移率和强磁场条件下, 磁光吸收谱可以观察到来自相邻郎道能级和相同自旋间的两个主吸收峰。随着电子浓度、外磁场以及自旋轨道耦合强度的不同可以相应地调制吸收谱强度和峰位等。另外, 由于朗道能级的混合, 使磁光谱出现自旋反转的跃迁, 但由于不同自旋态的电子波函数的重叠很小, 此跃迁对磁光吸收谱的贡献很小。     

Simulation of electrical properties of InxAl1-xN/AlN/GaN high electron mobility transistor structure

Electrical properties of In_x Al_1-xN/AlN/GaN structure are investigated by solving coupled Schr（o|¨）dinger and Poisson equations self-consistently.The variations in internal polarizations in In_xAl_1-xN with indium contents are studied and the total polarization is zero when the indium content is 0.41.Our calculations show that the twodimensional electron gas（2DEG） sheet density will decrease with increasing indium content.There is a critical thickness for AIN.The 2DEG sheet density will increase with In_xAl_1-xN thickness when the AIN thickness is less than the critical value.However,once the AIN thickness becomes greater than the critical value,the 2DEG sheet density will decrease with increasing barrier thickness.The critical value of AIN is 2.8 nm for the lattice-matched In_0.18Al_0.82N/AlN/GaN structure.Our calculations also show that the critical value decreases with increasing indium content.     

Characteristics study of 2DEG transport properties of AlGaN/GaN and AlGaAs/GaAs-based HEMT

Growth of wide bandgap material over narrow bandgap material, results into a two dimensional electron gas (2DEG) at the heterointerface due to the conduction band discontinuity. In this paper the 2DEG transport properties of AlGaN/GaN-based high electron mobility transistor (HEMT) is discussed and its effect on various characteristics such as 2DEG density, C-V characteristics and Sheet resistances for different mole fractions are presented. The obtained results are also compared with AlGaAs/GaAs-based HEMT for the same structural parameter as like AlGaN/GaN-based HEMT. The calculated results of electron sheet concentration as a function of the Al mole fraction are in excellent agreement with some experimental data available in the literature.     

A new low-noise AlGaAs/GaAs 2DEG FET with a surface undoped layer

A high-performance N-AlGaAs/GaAs selectively doped two-dimensional electron gas (2DEG) FET with a surface undoped layer has been designed and demonstrated. Simple analysis based on the short-channel approximation revealed that an increase in a total layer thickness between a gate electrode and 2DEG at a hetero-interface results in a higher cutoff frequency and a lower noise figure than conventional 2DEG FET's. This is because the gate capacitance can be markedly reduced without a significant decrease in the transconductance owing to a parasitic source resistance. The surface undoped layer intentionally employed in this work can permit the total layer thickness to increase, i.e., the gate capacitance to reduce, without changes in the 2DEG density and in the source resistance. This structure also gives high gate breakdown voltage because of a small neutral region in n- (AlGa)As and a low surface electron field, which possibly yields excellent performance 2DEG FET's for practical use. Fabricated (AlGa)As/ GaAs 2DEG FET's exhibited noticeable room-temperature performances of 0.95-dB noise figure with 10.3-dB associated gain at 12- and 45-GHz cutoff frequency. These are the best data ever reported for 0.5-µm gate length FET's.     

量子点场效应单光子探测器二维电子气电子迁移率分析

设计了一种基于场效应晶体管的量子点场效应单光子探测器,利用二维弛豫时间的近似理论建立了二维电子气电子迁移率的散射模型,通过求解量子点场效应单光子探测器GaAs/AlxGa1-xAs二维电子气系统电子和声子相互作用的Hamiltonian函数,得到了不同温度、不同Al组分以及不同二维电子气电子面密度条件下晶格振动散射对探测器二维电子气电子迁移率的影响.仿真结果显示,提高二维电子气的电子面密度浓度和适当增大Al组分,并降低工作温度,有助于探测器获得更高的二维电子气电子迁移率.     

InP-HEMT中复合沟道的设计与生长

设计并生长了带有复合沟道的InP基HEMT材料,该材料具有较高的二维电子气浓度和迁移率。在使用In_xGa_(1-x)As/In_(0.53)Ga_(0.47)As复合沟道时,当In组分等于0.7时得到较好的沟道输运性能;在使用InAs复合沟道时,得到了二维电子气浓度为2.3×10~(12)/cm~2、室温迁移率高达13600 cm~2/V·s的性能优良的HEMT材料。     

Si/Si_(1-x)Ge_x HEMT异质结层的结构与二维电子气密度的关系

从晶格匹配及能带阶跃角度讨论了设计一个 n沟 Si/Si1-x Gex HEMT异质结层的原理及方法 ,对 K.Ismail器件进行了分析和计算 ,所得 2 DEG的 ns与实验结果基本相符 ,并利用该设计理论对 K. Ismail器件的异质结结构进行了优化改进 ,提高了器件 2 DEG的 ns。     

沟道电场分布对AlN/GaN HFETs极化库仑场散射的影响

Based on the measured capacitance–voltage(C–V) curves and current–voltage(I–V) curves for the prepared differently-sized Al N/Ga N heterostructure field-effect transistors(HFETs), the I–V characteristics of the Al N/Ga N HFETs were simulated using the quasi-two-dimensional(quasi-2D) model. By analyzing the variation in the electron mobility for the two-dimensional electron gas(2DEG) with the channel electric field, it is found that the different polarization charge distribution generated by the different channel electric field distribution can result in different polarization Coulomb field(PCF) scattering. The 2DEG electron mobility difference is mostly caused by the PCF scattering which can reach up to 899.6 cm2/(V s)(sample a), 1307.4 cm2/(V s)(sample b),1561.7 cm2/(V s)(sample c) and 678.1 cm2/(V s)(sample d), respectively. When the 2DEG sheet density is modulated by the drain–source bias, the electron mobility for samples a, b and c appear to peak with the variation of the 2DEG sheet density, but for sample d, no peak appears and the electron mobility rises with the increase in the2 DEG sheet density.