AlGaN/AlN/GaN HEMT结构2DEG的光致发光谱

AlGaN/GaN HEMT结构材料主要用于研制微电子器件,对其发光性质的研究相对较少。通过对AlGaN/GaN HEMT结构材料的光致发光谱(PL)研究,观测到了AlGaN势垒层中Al组分为40%的AlGaN/AlN/GaN结构中二维电子气(2DEG)光致发光及其能级分裂现象。在4.5 K低温下,其2DEG发光峰在GaN带边峰能量以下30和40 meV处分裂成两个峰位,直至温度持续升高至40 K后消失。根据GaN价带顶部在单轴晶格场和自旋-轨道耦合共同作用下的能级分裂理论,因自旋-轨道耦合引起的2DEG发光峰两个分裂能级差约为10 meV,与实验测得的结果一致,因此实验观测到的2DEG发光峰的分裂现象是由于氮化镓价带能级的自旋-轨道耦合而形成的。

Analytical model of non-uniform charge distribution within the gated region of GaN HEMTs

A physics-based analytical expression that predicts the charge,electrical field and potential distributions along the gated region of the GaN HEMT channel has been developed.Unlike the gradual channel approximation(GCA),the proposed model considers the non-uniform variation of the concentration under the gated region as a function of terminal applied volt-ages.In addition,the model can capture the influence of mobility and channel temperature on the charge distribution trend.The comparison with the hydrodynamic(HD)numerical simulation showed a high agreement of the proposed model with numerical data for different bias conditions considering the self-heating and quantization of the electron concentration.The ana-lytical nature of the model allows us to reduce the computational and time cost of the simulation.Also,it can be used as a core expression to develop a complete physics-based transistorⅣmodel without GCA limitation.

RF-MBE Grown AlGaN/GaN HEMT Structure with High Al Content

A Si doped AlGaN/GaN HEMT structure with high Al content (x=43%) in the barrier layer is grown on sapphire substrate by RF-MBE.The structural and electrical properties of the heterostructure are investigated by the triple axis X-ray diffraction and Van der Pauw-Hall measurement,respectively.The observed prominent Bragg peaks of the GaN and AlGaN and the Hall results show that the structure is of high quality with smooth interface.The high 2DEG mobility in excess of 1260cm2/(V·s) is achieved with an electron density of 1.429×10 13cm -2 at 297K,corresponding to a sheet-density-mobility product of 1.8×10 16V -1·s -1.Devices based on the structure are fabricated and characterized.Better DC characteristics,maximum drain current of 1.0A/mm and extrinsic transconductance of 218mS/mm are obtained when compared with HEMTs fabricated using structures with lower Al mole fraction in the AlGaN barrier layer.The results suggest that the high Al content in the AlGaN barrier layer is promising in improving material electrical properties and device performance.

具有栅源间本征GaN调制层的AlGaN/GaN HEMT

为解决常规AlGaN/GaN高电子迁移率晶体管(HEMT)因源极电子注入栅极右侧高场区造成的雪崩击穿,并提高器件的击穿电压,提出了一种具有栅源间本征GaN(i-GaN)调制层的新型AlGaN/GaN HEMT结构。新结构器件在反向耐压时将调制层下方部分区域的二维电子气(2DEG)完全耗尽,扩展了沟道的夹断区,有效阻止了源极电子向栅极右侧高场区的注入。仿真结果表明,通过设置适当的调制层长度和厚度,器件的击穿电压可从常规结构的862 V提升至新结构的1 086 V,增幅达26%。同时,GaN调制层会微幅增大器件的比导通电阻,对阈值电压也具有一定的提升作用。

AlGaN/GaN HEMT势垒层厚度影响的模拟及优化

完成了对AlGaN/GaN高电子迁移率晶体管(HEMT)的结构设计及器件物理特性的验证等工作。使用TCAD软件完成了该器件直流特性及微波特性等性能的模拟。建立该器件的极化效应模型是本项研究的重点。完成了对异质结条件下诸多模型参数的筛选及修正,得到了符合理论的模拟结果。器件特性的验证与优化基于势垒层厚度h的变化展开,研究结果显示:漏极电流随h值的增加而增加,当h值超过40nm时,因二维电子气浓度上升缓慢而使漏极电流趋于饱和;跨导随h值的减小而增大,h每降低10nm,跨导约增大37mS/mm;势垒层厚度对高频特性的影响较小。

Electrical characteristics of AlInN/GaN HEMTs under cryogenic operation

Electrical properties of an AIlnN/GaN high-electron mobility transistor （HEMT） on a sapphire substrate are investigated in a cryogenic temperature range from 295 K down to 50 K. It is shown that drain saturation current and conductance increase as transistor operation temperature decreases. A self-heating effect is observed over the entire range of temperature under high power consumption. The dependence of channel electron mobility on electron density is investigated in detail. It is found that aside from Coulomb scattering, electrons that have been pushed away from the AIInN/GaN interface into the bulk GaN substrate at a large reverse gate voltage are also responsible for the electron mobility drop with the decrease of electron density.

Modeling of Noise Power Spectral Density Analysis for GaN/AlGaN HEMT

Nano Technology is the branch of technology that deals with dimensions and tolerances in terms of nanometers. In this paper, the electrical characteristics analysis is determined for the Nano-GaN HEMT and Micro-GaN HEMT and also power spectrum density is determined for GaN Nano-HEMT by reducing the gate length Lg in nm range. The GaN Nano HEMT is producing high current comparing to Micro GaN HEMT. Accuracy of the proposed analytical model results is verified with simulation results.

GaN HEMT光滑动态模型的建模与验证

阐述氮化镓高电子迁移率晶体管的一种光滑行为模型,以连续光滑的曲线来描述晶体管的动态特性,使用GetData提取曲线图数据,使用MATLAB中的Curve Fitting Tool对方程拟合提取参数,使用Simulink对模型进行验证,最终获得较为准确的晶体管模型。对比其他种类的模型,提出的光滑行为模型具有等效电路简洁、拟合参数数量较少等优势。

Theoretical analytic model for RESURF AlGaN/GaN HEMTs

In this paper, we propose a two-dimensional(2D) analytic model for the channel potential and electric field distribution of the RESURF AlGaN/GaN high electron mobility transistors(HEMTs). The model is constructed by two-dimensional Poisson's equation with appropriate boundary conditions. In the RESURF AlGaN/GaN HEMTs, we utilize the RESURF effect generated by doped negative charge in the AlGaN layer and introduce new electric field peaks in the device channels,thus, homogenizing the distribution of electric field in channel and improving the breakdown voltage of the device. In order to reveal the influence of doped negative charge on the electric field distribution, we demonstrate in detail the influences of the charge doping density and doping position on the potential and electric field distribution of the RESURF AlGaN/GaN HEMTs with double low density drain(LDD). The validity of the model is verified by comparing the results obtained from the analytical model with the simulation results from the ISE software. This analysis method gives a physical insight into the mechanism of the AlGaN/GaN HEMTs and provides reference to modeling other AlGaN/GaN HEMTs device.

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

A new surface-potential-based model for A1GaN/A1N/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 A1GaN/A1N/GaN HEMT is rewritten. Compared with TCAD simulations, the DC characteristics of A1GaN/AIN/GaN HEMT are faithfully reproduced by the new model.

A complete and accurate surface-potential based large-signal model for compound semiconductor HEMTs

A complete and accurate surface potential based large-signal model for compound semiconductor HEMTs is presented. A surface potential equation resembling the one used in conventional MOSFET models is achieved. The analytic solutions from the traditional surface potential theory that developed in MOSFET models are inherited. For core model derivation, a novel method is used to realize a direct application of the standard surfacepotentialmodelofMOSFETsforHEMTmodeling,withoutbreakingthemathematicstructure.Thehigh-order derivatives of I–V /C–V remain continuous, making the model suitable for RF large-signal applications. Furthermore, the self-heating effects and the transconductance dispersion are also modelled. The model has been verified through comparison with measured DC IV, Gummel symmetry test, CV, minimum noise figure, small-signal Sparameters up to 66 GHz and single-tone input power sweep at 29 GHz for a 475 m0.1 m InGaAs/GaAs power pHEMT, fabricated at a commercial foundry.

基于GaN基HEMT结构的传感器件研究进展

GaN基高电子迁移率晶体管(HEMT)具有异质结界面处的高二维电子气(2DEG)浓度、宽禁带、高击穿电压、稳定的化学性质以及高的电子迁移率,这些特性使它发展起来的传感器件在灵敏度、响应速度、探测面、适应恶劣环境上具备了显著的优点。本文首先围绕GaN基HEMT的基本结构发展起来的两类研究成熟的传感器,对其结构、工作机理、工作进展以及优缺点进行了探讨与总结;而后,着重从改变器件材料及优化栅结构与栅上材料的角度,阐述了3种GaN基HEMT新型传感器的最新进展,其中,从材料体系、关键工艺、探测结构、原理及新机理方面重点介绍了GaN基HEMT光探测器;最后,探索了GaN基HEMT传感器件未来的发展方向。

A revised approach to Schottky parameter extraction for GaN HEMT

We carry out a thermal storage research on GaN HEMT at 350℃for 48 h,and a recess phenomenon is observed in the low voltage section of Schottky forward characteristics.The decrease of 2DEG density will be responsible for the recess phenomenon.Because the conventional method is not suitable for this kind of curve,a revised approach is presented by analyzing the back-to-back Schottky junction energy band to extract Schottky parameters, which leads to a consistent fit effect.

An Explicit Surface-Potential Based Biaxial Strained-Si n-MOSFET Model for Circuit Simulation

In this paper, a charge sheet surface potential based model for strained-Si nMOSFETs is presented and validated with numerical simulation. The model considers sub band splitting in the 2-DEG at the top heterointerface in SiGe layer and also the dependence of electron concentration at heterointerface with the gate oxide. The model is scalable with strained-Si material parameters with physically derived flat-band voltages. An explicit relation for surface potential as a function of terminal voltages is developed. The model is derived from regional charge-based approach, where regional solutions are physically derived. The model gives an accurate description of drain current both in the weak and strong inversion regions of operation. The results obtained from the model developed are benchmarked with commercial numerical device simulator and is found to be in excellent agreement.

A two-dimensional fully analytical model with polarization effect for off-state channel potential and electric field distributions of GaN-based field-plated high electron mobility transistor

In this paper, we present a two-dimensional （2D） fully analytical model with consideration of polarization effect for the channel potential and electric field distributions of the gate field-plated high electron mobility transistor （FP-HEMT） on the basis of 2D Poisson＇s solution. The dependences of the channel potential and electric field distributions on drain bias, polarization charge density, FP structure parameters, A1GaN/GaN material parameters, etc. are investigated. A simple and convenient approach to designing high breakdown voltage FP-HEMTs is also proposed. The validity of this model is demonstrated by comparison with the numerical simulations with Silvaco-Atlas. The method in this paper can be extended to the development of other analytical models for different device structures, such as MIS-HEMTs, multiple-FP HETMs, slant-FP HEMTs, etc.

RF and microwave characteristics of a 10 nm thick InGaN-channel gate recessed HEMT

A new depletion-mode gate recessed A1GaN/InGaN/GaN-high electron mobility transistor （HEMT） with 10 nm thickness of InGaN-channel is proposed. A growth of A1GaN over GaN leads to the formation of two- dimensional electron gas （2DEG） at the heterointerface. High 2DEG density （ns） is achieved at the heterointerface due to a strain induced piezoelectric effect between A1GaN and GaN layers. The electrons are confined in the InGaN-channel without spilling over into the buffer layer, which also reduces the buffer leakage current. From the input transfer characteristics the threshold voltage is obtained as -4.5 V and the device conducts a current of 2 A/mm at a drain voltage of 10 V. The device also shows a maximum output current density of 1.8 A/ram at Vds of 3 V. The microwave characteristics like transconductance, cut-off frequency, max frequency of oscillation and Mason＇s Unilateral Gain of the device are studied by AC small-signal analysis using a two-port network. The stability and power performance of the device are analyzed by the Smith chart and polar plots respectively. To our knowledge this proposed InGaN-channel HEMT structure is the first of its kind.

Analytical modeling of AlInSb/InSb MOS gate HEMT structure with improved performance

The performance of AlInSb/InSb heterostructure with various parameters is considered with T-Cad simulation.As the heterojunctions are having more advantageous properties that is a real support for so many application such as solar cells,semiconductor cells and transistors.Special properties of semiconductors are discussed here with various parameters that are depending up on the performance of accurate device[Pardeshi H.,Pati S.K.,Raj G.,Mohankumar N.,Sarkar C.K.,J.Semicond.33(12):124001-1–124001-7,2012].The maximum drain current density is achieved with improving the density of two-dimensional electron gas(2DEG)and with high velocity.High electron mobility transistor(HEMT)structure is used with the different combinations of layers which have different bandgaps.Parameters such as electron mobility,bandgap,dielectric constant,etc.,are considered differently for each layer[Zhang A.,Zhang L.,Tang Z.,IEEE Trans.Electron Devices 61(3):755–761,2014].The high electron mobility electrons are now widely used in so many applications.The proposed work of AlInSb/InSb heterostructure implements the same process which will be a promise for future research works.

基于表面势的HEMT模型分析

将表面势的概念引入GaAs高电子迁移率晶体管器件结构,以建立可精确描述HEMT器件输入/出特性的新模型。通过分析最基本的HEMT结构,参考Si基MOSFET中Pao-sah模型的分析方法,对沟道电荷利用泊松方程表述,并结合能带电压关系,建立HEMT器件中表面势(Φ_s)对于栅压(V_(GS))的关系。基于上述分析计算了沟道中电子的饱和点。根据推导所得方程,模型计算得到的某具体器件沟道面电荷密度(n_s)-栅压(V_(GS))关系曲线和基于T-CAD工具仿真结果在线性区得到很好的吻合。

基于单核细胞相关基因筛选颈动脉粥样硬化的诊断生物标记

目的筛选单核细胞相关基因(MRGs)作为颈动脉粥样硬化(CAS)中的诊断生物标记。方法从GEO数据库中获取“有和无CAS”患者的单核细胞的转录组数据,进行加权基因共表达网络分析(WGCNA),用limma包获得差异表达基因(DEGs);采用最小绝对收缩选择算子(LASSO)和支持向量机递归特征消除(SVM-RFE)算法推导CAS的诊断分子,对诊断分子构建列线图判断CAS患病的风险率,并绘制校正曲线对列线图进行验证,利用DrugBank数据库预测针对诊断分子的潜在药物;采集对照组(无CAS)和CAS组患者的外周血单核细胞样本,通过采用定量(qRT-PCR)检测其表达谱。结果共筛选到14369个枢纽(hub)基因和61个DEGs;6个基因被鉴定为差异表达单核细胞相关hub基因(DE-MRHGs),与免疫细胞、免疫反应、单核细胞和脂质代谢相关;LASSO回归和SVM-RFE算法显示,趋化因子(C-C-基元)配体3样蛋白1(CCL3L1)、趋化因子(C-C基元)配体4(CCL4)、高迁移率族蛋白B1(HMGB1)、趋化因子(C-C基元)配体3(CCL3)及双特异性磷酸酶1(DUSP1)被确定为CAS的诊断分子,这5个诊断分子构建的列线图结果显示其预测CAS的患病风险率达到99.9%以上,校准曲线说明列线图模型对患CAS具有较高的预测精度;依鲁替尼、丙酮酸乙酯、罗氟司特等11种化合物被确定为潜在的靶向诊断分子的药物;qRT-PCR实验验证结果显示,与对照组相比,CCL3L1、CCL4、CCL3和DUSP1在CAS中呈低表达(P<0.001),HMGB1在CAS组中呈高表达(P<0.05)。结论CCL3L1、CCL4、HMGB1、CCL3和DUSP1这5个单核细胞相关基因组成的的生物标志物可作为CAS的诊断和潜在的治疗靶点。

GaN基高电子迁移率晶体管的质子辐照效应研究

文章研究了A1GaN/GaN高电子迁移率晶体管(HEMT)的质子辐照效应。在3MeV质子辐照下,采用三种不同辐照剂量6×10^(14),4×10^(14)和1×10^(15)protons/cm^2。在最高辐照剂量下,漏极饱和电流下降了20%,最大跨导降低了5%。随着剂量增加,阈值电压向正向漂移,栅泄露电流增加。AlGaN/GaN HEMT电学特性的退化主要是由辐照引入的位移损伤引起的。从SRIM软件计算出空位密度,将Ga空位对应的能级引入Silvaco器件仿真软件中,仿真结果与实验结果相匹配。Hall测试结果显示二维电子气(2DEG)浓度和迁移率在辐照后有所降低。