电流增益截止频率为236GHz的InAIN/GaN高频HEMT

研制了高电流增益截止频率(fT)的InAlN/GaN高电子迁移率晶体管(HEMT).采用金属有机化学气相沉积(MOCVD)再生长n+GaN非合金欧姆接触工艺将器件源漏间距缩小至600 nm,降低了源、漏寄生电阻,有利于改善器件的寄生效应;使用低压化学气相沉积(LPCVD)生长SiN作为栅下介质,降低了InAlN/GaN HEMT栅漏电;利用电子束光刻实现了栅长为50 nm的T型栅.此外,还讨论了寄生效应对器件fT的影响.测试结果表明,器件的栅漏电为3.8 μA/mm,饱和电流密度为2.5 A/mm,fT达到236 GHz.延时分析表明,器件的寄生延时为0.13 ps,在总延时中所占的比例为19％,优于合金欧姆接触工艺的结果.     

fT为102 GHz的蓝宝石衬底AlGaN/GaN高电子迁移率晶体管

研究了一款高性能的AlGaN/GaN高电子迁移率晶体管器件(HEMT),器件基于在蓝宝石衬底上外延生长的AlGaN/GaN异质结构HEMT材料,器件栅长为86 nm,源漏间距为0.8μm。电子束光刻实现T型栅和源漏,保证了器件小的栅长和高的对准精度。制备的器件显示了良好的直流特性和射频特性,在栅偏压为0 V时漏电流密度为995 mA/mm,在栅源电压Vgs为-4.5 V时,最大峰值跨导为225 mS/mm;器件的电流增益截止频率fT和最大振荡频率fmax分别为102和147 GHz。高fT值一方面得益于小栅长,另一方面由于小源漏间距减小了源漏沟道电阻。     

超薄势垒InAlN/GaN HFET器件高频特性分析

采用二次外延重掺杂n+ GaN实现非合金欧姆接触,并通过优化干法刻蚀和金属有机化学气相沉积(MOCVD)外延工艺,有效降低了欧姆接触电阻.将非合金欧姆接触工艺应用于InAlN/GaN异质结场效应晶体管(HFET)器件制备,器件的有效源漏间距缩小至600 nm.同时,结合40 nm T型栅工艺,制备了高电流截止频率(fT)和最大振荡频率(fmax)的InAlN/GaN HFET器件.结果显示减小欧姆接触电阻和栅长后,器件的电学特性,尤其是射频特性得到大幅提升.栅偏压为0V时,器件最大漏源饱和电流密度达到1.88 A/mm;直流峰值跨导达到681 mS/mm.根据射频小信号测试结果外推得到器件的fT和fmax同为217 GHz.     

一种新的AlGaN/GaN HEMT半经验直流特性模型

在EEHEMT1模型的基础上给出一种新的A1GaN/GaN HEMT半经验直流特性模型,考虑了栅源电压对膝点电压的影响,得到描述AlGaN/GaN HEMT器件I-Ⅴ特性的方程.此模型可以应用于蓝宝石和SiC两种不同衬底AlGaN/GaN HEMT器件的I-Ⅴ特性模拟.仿真结果和实验测量结果拟合误差小于3%.     

一种新的AlGaN/GaN HEMT半经验直流特性模型

在EEHEMT1模型的基础上给出一种新的A1GaN/GaN HEMT半经验直流特性模型,考虑了栅源电压对膝点电压的影响,得到描述AlGaN/GaN HEMT器件I-Ⅴ特性的方程.此模型可以应用于蓝宝石和SiC两种不同衬底AlGaN/GaN HEMT器件的I-Ⅴ特性模拟.仿真结果和实验测量结果拟合误差小于3%.     

干法刻蚀和氢等离子体处理制备增强型p-GaN栅AlGaN/GaN HEMT特性

增强型p-GaN栅AlGaN/GaN高电子迁移率晶体管(HEMT)的栅与源漏之间的沟道特性对器件性能具有重要的影响.在同一晶圆衬底上,采用干法刻蚀和氢等离子体处理栅与源、漏之间的p-GaN,制备增强型p-GaN栅AlGaN/GaN HEMT.对器件静态、动态特性和栅极漏电特性进行研究,采用两种方法制备的器件均具有较高的击穿电压(＞850 V@10 μA/mm).通过氢等离子体处理制备的器件的方块电阻较大,导致输出电流密度较低,在动态特性和栅极漏电方面具有明显的优势,氢等离子体处理技术提高了界面态的缺陷激活能,从而实现了较低的栅极反向漏电.     

AlGaN/GaN 高电子迁移率晶体管在施加阶梯电压应力之后的参数和特性自变化机制

研究了在AlGaN/GaN高电子迁移率晶体管的栅极施加阶梯电压应力之后器件参数和特性的自变化现象。在去除应力之后每5分钟测量一次器件。大信号寄生源（漏）电阻、转移特性、阈值电压、漏源电流、栅-源（漏）反向电流-电压特性在去除应力后发生自发变化。自变化的时间常数大约为25-27分钟。在该过程里,栅-源（漏）电容-电压特性保持稳定。当器件被施加应力时,电子被表面态和AlGaN势垒层陷阱捕获。AlGaN势垒层陷阱所捕获的电子在10秒内释放了出去。表面态释放电子持续发生在整个测量过程中,导致了测量结果的自变化现象。     

AlGaN/GaN HEMT器件的研制

介绍了AlGaN/GaN HEMT器件的研制及室温下器件特性的测试.漏源欧姆接触采用Ti/Al/Pt/Au,肖特基结金属为Pt/Au.器件栅长为1μm,获得的最大跨导为120mS/mm,最大的漏源饱和电流密度为0.95A/mm.     

低导通电阻和栅漏电的高性能InAlN/GaN HEMT

本文制备了100nm栅长的InAlN/GaN HEMT。通过氧处理和优化欧姆接触获得了高性能的InAlN/GaN HEMT。所制备的器件在栅压偏置为2V时,漏端输出电流密度达到2.18A/mm。器件的导通电阻为1.49Ω*mm。与常规器件相比,器件的栅漏电下降了两个数量级。器件也获得良好的射频特性,电流截止频率和最高震荡频率分别为81GHz和138GHz。根据现有的报道,这是国内较早报道GaN基HEMT电流密度超过2A/mm。     

fT为350 GHz的InAlN/GaN HFET高频器件研究

采用再生长n+ GaN非合金欧姆接触工艺研制了具有高电流增益截止频率(fT)的InAlN/GaN异质结场效应晶体管 (HFETs),器件尺寸得到有效缩小,源漏间距减小至600 nm.通过优化干法刻蚀和n+ GaN外延工艺,欧姆接触总电阻值达到0.16 Ω·mm,该值为目前金属有机化学气相沉积(MOCVD)方法制备的最低值.采用自对准电子束曝光工艺实现34 nm直栅.器件尺寸的缩小以及欧姆接触的改善,器件电学特性,尤其是射频特性得到大幅提升.器件的开态电阻(Ron)仅为0.41 Ω·mm,栅压1 V下,漏源饱和电流达到2.14 A/mm.此外,器件的电流增益截止频率(fT)达到350 GHz,该值为目前GaN基HFET器件国内报道最高值.     

Improved temperature model of AlGaN/GaN HEMT and device characteristics at variant temperature

In this paper, an improved temperature model for AlGaN/GaN high electron mobility transistor (HEMT) is presented. Research is being conducted for a high-performance building block for high frequency applications that combine lower costs with improved performance and manufacturability. The effects of channel conductance in the saturation region and the parasitic resistance due to the undoped GaN buffer layer have been included. The effect of both spontaneous and piezoelectric polarization induced charges at the AlGaN/GaN heterointerface has been incorporated. The proposed model is used to determine the transfer characteristics, output current-voltage characteristics and small-signal microwave parameters of HEMTs. The investigated temperature range is from 100–600 K. The small signal microwave parameters have been evaluated to determine the unity current gain cut-off frequency (f _T ). High f _T (10–70 GHz) values and high current levels (～550 mA/mm) are achieved for a 1 μm AlGaN/GaN HEMTs. A custom DC measurement system is used to facilitate the DC characterization of the unpackaged GaN HEMT test device. The calculated critical parameters and the simulation results suggest that the performance of the proposed device degrades at elevated temperatures.     

一种紧凑的GaN高电子迁移率晶体管大信号模型拓扑

GaN高电子迁移率晶体管（HEMT）以其复杂的器件特性使其大信号建模变得十分困难,尽管EEHEMT、Angelov等模型结构曾经成功应用于GaAs HEMT/MESFET的大信号模型,但当它们被用于GaN HEMT建模时却不再准确和完备.面向GaN HEMT器件的大信号模型,本文提出了一种紧凑的模型拓扑,此模型拓扑综合了GaN HEMT器件的直流电压-电流（I-V）特性、非线性电容、寄生参数、栅延迟漏延迟与电流崩塌、自热效应以及噪声等特性.经验证此模型拓扑在仿真中具有很好的收敛性,适用于GaN HEMT器件的大信号模型的建立,满足GaN基微波电路设计对器件模型的需求.     

Modeling and simulation of enhancement mode p-GaN Gate AlGaN/GaN HEMT for RF circuit switch applications

An enhancement mode p-GaN gate AlGaN/GaN HEMT is proposed and a physics based virtual source charge model with Landauer approach for electron transport has been developed using Verilog-A and simulated using Cadence Spectre, in order to predict device characteristics such as threshold voltage, drain current and gate capacitance. The drain current model incorporates important physical effects such as velocity saturation, short channel effects like DIBL (drain induced barrier lowering), channel length modulation (CLM), and mobility degradation due to self-heating. The predicted I_d-V_ds, I_d-V_gs, and C-V characteristics show an excellent agreement with the experimental data for both drain current and capacitance which validate the model. The developed model was then utilized to design and simulate a single-pole single-throw (SPST) RF switch.     

AlGaN/GaN HEMT小信号模型参数提取算法

本文采用了新型的22元件AlGaN/GaN HEMT小信号等效电路模型,较传统的模型,增加了栅漏电导Ggdf和栅源电导Ggsf来表征GaN HEMT的栅极泄漏电流。同时针对新型的栅场板、源场板结构器件,提出了一种改进的寄生电容参数提取方法,使之适用于提取非对称器件的小信号模型参数。为验证此模型,获得了S参数的测试结果和模型仿真结果,此二者的吻合度较高,表明新型的22元件小信号模型精确、稳定而且物理意义明确。     

寄生电感对低压增强型GaN HEMT开关行为的影响

寄生电感是影响功率管开关特性的重要因素之一,开关频率越高,寄生电感对低压增强型氮化镓高电子迁移率晶体管(GaN HEMT)的开关行为影响越深,使其无法发挥高速开关的性能优势。通过建立数学模型,理论分析了考虑各部分寄生电感后增强型GaN HEMT的开关过程,并推导了各阶段的持续时间和影响因素,然后通过建立双脉冲测试平台,对各部分寄生电感对开关特性的具体影响进行了实验验证。实验结果表明,寄生电感会使开关过程中的电流、电压出现振荡,影响开关速度和可靠性,并且各部分寄生电感对增强型GaN HEMT的开关过程影响程度不同,在实际PCB布局受到物理限制时,需要根据设计目标优化布局,合理分配各部分寄生电感以获得最优的开关性能。     

Analytical HFET $I$– $V$ Model in Presence of Current Collapse

A compact analytical model of short-channel AlGaN/GaN HEMTs in the presence of a current collapse is presented. The model is based on an experimentally established trapping mechanism at the gate edges and relies on significant differences between the characteristic carrier capture-escape times and typical RF signal periods. For the first time, we implement the theory describing electric field distributions in the HEMT gate-to-drain spacing region, with and without trapped charge distributions. By consequently accounting for velocity saturation effects in gated and trapped regions of the device, the presented model shows good agreement with the experimental data. The model uses a minimal number of fitting parameters, most of which are physical parameters describing velocity-field dependence of the carriers.     

A compact C–V model for 120 nm AlGaN/GaN HEMT with modified field dependent mobility for high frequency applications

We present a theoretical model of AlGaN/GaN high electron mobility transistor (HEMT) that includes the effect of spontaneous and piezoelectric polarization. Present model also incorporates the effect of mole fraction dependent mobility, saturation velocity and the accurate 2-DEG density in HEMT as a function of gate voltage in subthreshold, linear and saturation regimes. This paper reports a detailed 2-D analysis of capacitance–voltage (C–V) characteristics. The contribution of various capacitances including fringing field capacitance on the performance of the device is also shown. The model further predicts the transconductance, drain conductance and frequency of operation and is in close proximity with the experimental data which confirms the validity of proposed model.     

AlGaN/GaN高电子迁移率晶体管小信号等效电路的参数提取

本文在高电子迁移率晶体管(HEMT)小信号等效电路模型的基础上,考虑了AlGaN/GaN HEMT的结构特性,具体分析了寄生参数和本征参数的提取方法.采用这些方法,实际测量了5～10 GHz频率下HEMT器件的小信号S参数并提取了它的电学参数,S参数的计算值与实际测量值进行了比较.实验结果表明此方法简单易行,较为精确.     

A surface-potential-based model for AlGaN/AlN/GaN HEMT

A new surface-potential-based model for AlGaN/AlN/GaN high electron mobility transistor(HEMT) is proposed in this paper. Since the high polarization effects caused by AlN interlayer favorably influence the two dimensional electron gas(2DEG) and scattering mechanisms, we first add spontaneous and piezoelectric charge terms to the source equation of surface-potential, and a mobility model for AlGaN/AlN/GaN HEMT is rewritten. Compared with TCAD simulations, the DC characteristics of AlGaN/AlN/GaN HEMT are faithfully reproduced by the new model.