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。

功率PHEMT的直流特性研究

描述了高电子迁移率晶体管的作用、工作原理及发展概况，叙述了器件特性。制作出了栅长为１μｍ的ＰＨＥＭＴ样品，它的最大跨导为１７０ｍＳ／ｍｍ，击穿电压为４Ｖ，最大电流密度为２７０ｍＡ／ｍｍ，阈值电压为１．５Ｖ。

HEMT的材料结构和二维电子气浓度的关系

给出了ＨＥＭＴ和ＰＨＥＭＴ的数学－物理模型。系统地描述了材料的隔离层、平面调制掺杂层、势垒耗尽层等材料结构尺寸和异质结界面二维电子气浓度及器件沟道电流之间的相互关系。

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。

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。

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.

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。

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.

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.

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.

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.

Breakdown voltage analysis of Al_(0.25)Ga_(0.75)N/GaN high electron mobility transistors with partial silicon doping in the AlGaN layer

In this paper,two-dimensional electron gas（2DEG） regions in AlGaN/GaN high electron mobility transistors（HEMTs） are realized by doping partial silicon into the AlGaN layer for the first time.A new electric field peak is introduced along the interface between the AlGaN and GaN buffer by the electric field modulation effect due to partial silicon positive charge.The high electric field near the gate for the complete silicon doping structure is effectively decreased,which makes the surface electric field uniform.The high electric field peak near the drain results from the potential difference between the surface and the depletion regions.Simulated breakdown curves that are the same as the test results are obtained for the first time by introducing an acceptor-like trap into the N-type GaN buffer.The proposed structure with partial silicon doping is better than the structure with complete silicon doping and conventional structures with the electric field plate near the drain.The breakdown voltage is improved from 296 V for the conventional structure to 400 V for the proposed one resulting from the uniform surface electric field.

一种具有N埋层的AlGaN/GaN高电子迁移率晶体管

为了进一步提高GaN HEMT器件的击穿电压,并保持低的导通电阻,文中提出了一种具有N型GaN埋层的AlGaN/GaN HEMT。该埋层通过调整器件的电场分布,降低了高场区的电场峰值,从而降低器件关断时的泄漏电流。该埋层使得栅漏之间的横向沟道电场分布更加均匀,提高了器件的击穿电压。通过Sentaurus TCAD仿真发现,N型GaN埋层可以明显改善器件的击穿电压。相比于传统结构530 V的击穿电压,新结构的击穿电压达到了892 V,提高了68%。此外,N型GaN埋层没有影响到器件的导通特性,使得器件保留了低的特征导通电阻。以上结果说明,该结构在功率器件领域具有良好的应用前景。

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。

高电子迁移率晶体管的光照特性分析

以光照下耗尽型 ＡｌＧａＡｓ／ＧａＡｓ高电子迁移率晶体管为例，考虑了光生载流子对半导体内电荷密度的影响和光压效应，采用器件的电荷控制模型，分析了光照对器件夹断电压、二维电子气（２－ＤＥＧ）浓度、Ｉ—Ｖ特性以及跨导的影响．与无光照的情况相比较，夹断电压变小（绝对值变大），二维电子气浓度增大，从而提高了器件的电流增益．跨导对光照不敏感．

Simulation of electrical properties of In_xAl_(1-x)N/AlN/GaN high electron mobility transistor structure

Electrical properties of In_x Al_（1-x）N/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-x）N 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-x）N 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_（0.18）Al_（0.82）N/AlN/GaN structure.Our calculations also show that the critical value decreases with increasing indium content.