磷化铟复合沟道高电子迁移率晶体管击穿特性研究

用密度梯度量子模型定量研究了磷化铟(InP)复合沟道高电子迁移率晶体管(HEMT)的击穿特性，考虑了复合沟道内碰撞电离以及沟道量子效应，重点研究了器件击穿电压随In_0.7Ga_0.3As沟道厚度的变化关系，提出了提高击穿电压的方法，采用商用器件模拟软件Sentaurus模拟了器件的开态击穿电压，对比了实验和模拟的结果. 研究表明：适当减小In_0.7Ga_0.3As沟道层的厚度可以在保持器件饱和电流基本不变的前提下大幅度提高开态击穿电压，这对于提高InP基HEMT的功率性能具有重要意义. 关键词： 磷化铟 高电子迁移率晶体管 密度梯度模型 击穿     

磷化铟高电子迁移率晶体管外延结构材料抗电子辐照加固设计

为研究磷化铟高电子迁移率晶体管(InP HEMT)外延结构材料的抗电子辐照加固设计的效果,本文采用气态源分子束外延法制备了系列InP HEMT外延结构材料.针对不同外延结构材料开展了1.5 MeV电子束辐照试验,在辐照注量为2×10¹⁵ cm^-2条件下,并测试了InP HEMT外延结构材料二维电子气辐照前后的电学特性,获得了辐照前后不同外延结构InP HEMT材料二维电子气归一化浓度和电子迁移率随外延参数的变化规律,分析了InP HEMT二维电子气辐射损伤与Si-δ掺杂浓度、InGaAs沟道厚度和沟道In组分以及隔离层厚度等结构参数的关系.结果表明:Si-δ掺杂浓度越大,隔离层厚度较薄,InGaAs沟道厚度较大,沟道In组分低的InP HEMT外延结构二维电子气辐射损伤相对较低,具有更强的抗电子辐照能力.经分析原因如下:1)电子束与材料晶格发生能量传递,破坏晶格完整性,且在沟道异质界面引入辐射诱导缺陷,增加复合中心密度,散射增强导致二维电子气迁移率和浓度降低;2)高浓度Si-δ掺杂和薄隔离层有利于提高量子阱二维电子气浓度,降低二维电子气受辐射...     

赝配InGaAs/InAlAs调制掺杂异质结构的Shubnikov-de Haas振荡

赝配InGaAs/InAlAs调制掺杂异质结构可以获得很高的电子气面密度和电子迁移率，从而可以制成具有优越高频和低噪声特性的高电子迁移率晶体管(HEMT).文中报道InGaAs/InAlAs调制掺杂异质结构低温下纵向和横向磁阻随磁场强度变化的Shubnikov-de Haas(SdH)振荡和量子Hall效应.对SdH振荡曲线作了快速傅里叶变换，获得了二维电子气的能带结构和各能带上的电子气面密度.分析比较了顶层InGaAs不同掺杂情况对SdH振荡的影响，结果发现顶层InGaAs重掺杂，会对表面态起屏蔽作用， 关键词：     

基于凹槽结构抑制AlGaN/GaN高电子迁移率晶体管电流崩塌效应

基于双脉冲技术,研究了GaN缓冲层陷阱对AlGaN/GaN高电子迁移率晶体管电流崩塌效应的影响.结果表明,栅边缘漏侧的电场峰值使得沟道电子跃迁至缓冲层,并被缓冲层中的陷阱俘获是造成电流崩塌的主要原因之一.提出了势垒层局部凹槽结构,降低了栅边缘漏侧的电场峰值,使电场分布更加均匀,改善了器件的电流崩塌效应.与传统AlGaN/GaN高电子迁移率晶体管结构相比,新器件结构对电流崩塌效应的抑制作用至少提升了22.30%.     

InP基HEMT器件中二维电子气浓度及分布与沟道层厚度关系的理论分析

利用数值计算的方法研究了InP基高电子迁移率晶体管(HEMT)中沟道厚度对沟道中二维电子气(2DEG)性质的影响，并对产生这种影响的原因进行了深入探讨.计算结果表明，当沟道层厚度从10nm增加到40nm时，沟道中2DEG的密度几乎没有变化，但激发态和基态上的电子密度之比(R)先增加后减小.当沟道层厚度在20—25nm之间时，R达到最大.此结果可作为优化器件结构设计的依据. 关键词： HEMT 异质结 二维电子气 自洽计算     

高线性度Al_xGa_(1-x)N/Al_yGa_(1-y)N/GaN高电子迁移率晶体管优化设计

对新型复合沟道AlxGa1-xN/AlyGa1-yN/GaN高电子迁移率晶体管(HEMT)进行了优化设计.从半导体能带理论与量子阱理论出发,自洽求解了器件层结构参数对器件导带能级以及二维电子气(2DEG)中载流子浓度和横向电场的影响.用TCAD软件仿真得到了器件的层结构参数对器件性能的影响.结合理论分析和仿真结果确定了器件的最佳外延层结构Al0.31Ga0.69N/Al0.04Ga0.96N/GaNHEMT.对栅长1μm,栅宽100μm的器件仿真表明,器件的最大跨导为300mS/mm,且在栅极电压-2—1V的宽范围内跨导变化很小,表明器件具有较好的线性度;器件的最大电流密度为1300mA/mm,特征频率为11.5GHz,最大振荡频率为32.5GHz.     

AlGaAs/GaAs异质结中的平行电导效应

本文计算了AlGaAs/GaAs异质结在大栅压下,出现“平行电导效应”时的栅压与平行导电层中电荷的关系。由此给出了高电子迁移率晶体管(HEMT)在大栅压时跨导变化的特性,与实验进行了比较,符合较好。 关键词：     

LP-MOCVD生长温度对InGaAs性能的影响

众所周知,InGaAs在InP和GaAs二个系列材料中具有最大的载流子迁移率和最大的饱和速率,InGaAs/GaAs应变量子阱可以把GaAs的发射波长从0.83μm延伸到1.1μm[1],而InGaAs/InP量子阱激光器又可以实现1.1～1.8μm内任意波长发射[2],并且,InGaAs/InP探测器的响应波长范围为0.93μm～1.65μm[3],因此,它不论对高速电子器件如HBT和HEMT,还是光电子器件如激光器(LD)和探测器(PIN和APD)都具有极重要的意义。     

不同量子阱宽度的InP基In0.53GaAs/In0.52AlAs高电子迁移率晶体管材料二维电子气的性能研究

用Shubnikov-de Haas(SdH)振荡效应，研究了在1.4 K下不同量子阱宽度(10—35 nm)的InP基高电子迁移率晶体管材料的二维电子气特性.通过对纵向电阻SdH振荡的快速傅里叶变换分析，得到不同阱宽时量子阱中二维电子气各子带电子浓度和量子迁移率.研究发现，在Si掺杂浓度一定时，阱宽的改变对于量子阱中总的载流子浓度改变不大，但是随着阱宽的增加，阱中的电子从占据一个子带到占据两个子带，且第二子带上的载流子迁移率远大于第一子带迁移率.当量子阱宽度为20 nm时，处在第二子能级上的电子数与处在 关键词： 量子阱宽 二维电子气 Shubnikov-de Haas振荡 高电子迁移率晶体管     

新型双异质结高电子迁移率晶体管的电流崩塌效应研究

针对传统单结GaN基高电子迁移率晶体管器件性能受电流崩塌效应和自加热效应限制的困境,对新型A1GaN/GaN/InGaN/GaN双异质结高电子迁移率晶体管的直流性质展开了系统研究.采用基于热电子效应和自加热效应的流体动力模型,研究了器件在不同偏压下电流崩塌和负微分电导效应与GaN沟道层厚度的相关.研究发现具有高势垒双异质的沟道层能更好地将电子限制在沟道中,显著减小高电场下热电子从沟道层向GaN缓冲层的穿透能力.提高GaN沟道层厚度可以有效抑制电流崩塌和和负微分输出电导,进而提高器件在高场作用下的性能.所得结果为进一步优化双异质结高电子迁移率晶体管结构提供了新思路,可促进新型GaN高电子迁移率晶体管器件在高功率、高频和高温等无线通讯领域内的广泛应用.     

高电子迁移率晶体管放大器高功率微波损伤机理

在TCAD半导体仿真环境中,建立了0.25 m栅长的AlGaAs/InGaAs高电子迁移率晶体管(HEMT)低噪声放大器与微波脉冲作用的仿真模型,基于器件内部的电场强度、电流密度和温度分布的变化,研究了1 GHz的微波从栅极和漏极注入的损伤机理。研究结果表明,从栅极注入约40.1 dBm的微波时,HEMT内部峰值温度随着时间的变化振荡上升,最终使得器件失效,栅下靠源侧电流通道和强电场的同时存在使得该位置最容易损伤;从漏极注入微波时,注入功率的高低会使器件内部出现不同的响应过程,注入功率存在一个临界值,高于该值,器件有可能在第一个周期内损伤,损伤位置均在漏极附近。在1 GHz的微波作用下,漏极注入比栅极注入更难损伤。     

Analytical modeling and simulation of subthreshold behavior in nanoscale dual material gate AlGaN/GaN HEMT

A two-dimensional (2-D) analytical model for a Dual Material Gate (DMG) AlGaN/GaN High Electron Mobility Transistor (HEMT) has been developed to demonstrate the unique attributes of this device structure in suppressing short channel effects (SCEs). The model accurately predicts the channel potential, electric field variation along the channel, and sub-threshold drain current, taking into account the effect of lengths of the two gate metals, their work functions, barrier layer thicknesses, and applied drain biases. It is seen that the SCEs and hot carrier effects in DMG AlGaN/GaN HEMT are suppressed due to the work function difference of the two metal gates, thereby screening the drain potential variations by the gate near the drain. Besides, a more uniform electric field along the channel leads to improved carrier transport efficiency. The accuracy of the results obtained from our analytical model has been verified using ATLAS device simulations.     

An AlGaN/GaN HEMT with a reduced surface electric field and an improved breakdown voltage

A reduced surface electric field in an AlGaN/GaN high electron mobility transistor(HEMT) is investigated by employing a localized Mg-doped layer under the two-dimensional electron gas(2-DEG) channel as an electric field shaping layer.The electric field strength around the gate edge is effectively relieved and the surface electric field is distributed evenly as compared with those of HEMTs with conventional source-connected field plate and double field plate structures with the same device physical dimensions.Compared with the HEMTs with conventional sourceconnected field plates and double field plates,the HEMT with a Mg-doped layer also shows that the breakdown location shifts from the surface of the gate edge to the bulk Mg-doped layer edge.By optimizing both the length of Mg-doped layer,L m,and the doping concentration,a 5.5 times and 3 times the reduction in the peak electric field near the drain side gate edge is observed as compared with those of the HEMTs with source-connected field plate structure and double field plate structure,respectively.In a device with V GS = -5 V,L m = 1.5 μm,a peak Mg doping concentration of 8×10 17cm-3 and a drift region length of 10 μm,the breakdown voltage is observed to increase from 560 V in a conventional device without field plate structure to over 900 V without any area overhead penalty.     

具有部分本征GaN帽层新型AlGaN/GaN高电子迁移率晶体管特性分析

为了优化传统Al GaN/GaN高电子迁移率晶体管(high electron mobility transistors,HEMTs)器件的表面电场,提高击穿电压,本文提出了一种具有部分本征GaN帽层的新型Al GaN/GaN HEMTs器件结构.新型结构通过在Al GaN势垒层顶部、栅电极到漏电极的漂移区之间引入部分本征GaN帽层,由于本征GaN帽层和Al GaN势垒层界面处的极化效应,降低了沟道二维电子气(two dimensional electron gas,2DEG)的浓度,形成了栅边缘低浓度2DEG区域,使得沟道2DEG浓度分区,由均匀分布变为阶梯分布.通过调制沟道2DEG的浓度分布,从而调制了Al GaN/GaN HEMTs器件的表面电场.利用电场调制效应,产生了新的电场峰,且有效降低了栅边缘的高峰电场,Al GaN/GaN HEMTs器件的表面电场分布更加均匀.利用ISE-TCAD软件仿真分析得出:通过设计一定厚度和长度的本征GaN帽层,Al GaN/GaN HEMTs器件的击穿电压从传统结构的427 V提高到新型结构的960 V.由于沟道2DEG浓度减小,沟道电阻增加,使得新型Al GaN/GaN HEMTs器件的最大输出电流减小了9.2%,截止频率几乎保持不变,而最大振荡频率提高了12%.     

Modelling of high-temperature dark current in multi-quantum well structures from MWIR to VLWIR

In this paper, a model to calculate the dark current of quantum well infrared photodetectors at high-temperature regime is presented. The model is derived from a positive-definite quantum probability-flux and considers thermionic emission and thermally-assisted tunnelling as mechanisms of dark current generation. Its main input data are the wave functions obtained by time-independent Schrodinger equation and it does not require empirical parameters related to the transport of carriers. By means of this model, the dark current of quantum well infrared photodetectors at high-temperature regime is investigated with respect to the temperature, the barrier width, the applied electric field and the position of the first excited state. The theoretical results are compared with experimental data obtained from lattice-matched InAlAs/InGaAs, InGaAsP/InP on InP substrate and AlGaAs/GaAs structures with rectangular wells and symmetric barriers, whose absorption peak wavelengths range from MWIR to VLWIR. The corresponding results are in a good agreement with experimental data at different temperatures and at a wide range of applied electric field.     

Self-consistent analysis of double-δ-doped InAlAs/InGaAs/InP HEMTs

We have carried out a theoretical study of double-5-doped InAlAs/InGaAs/InP high electron mobility transistor （HEMT） by means of the finite differential method. The electronic states in the quantum well of the HEMT are calculated self-consistently. Instead of boundary conditions, initial conditions are used to solve the Poisson equation. The concentration of two-dimensional electron gas （2DEG） and its distribution in the HEMT have been obtained. By changing the doping density of upper and lower impurity layers we find that the 2DEG concentration confined in the channel is greatly affected by these two doping layers. But the electrons depleted by the Schottky contact are hardly affected by the lower impurity layer. It is only related to the doping density of upper impurity layer. This means that we can deal with the doping concentrations of the two impurity layers and optimize them separately. Considering the sheet concentration and the mobility of the electrons in the channel, the optimized doping densities are found to be 5 × 10^12 and 3× 10^12 cm^-2 for the upper and lower impurity layers, respectively, in the double-5-doped InAlAs/InGaAs/InP HEMTs.     

An AlGaN/GaN HEMT with reduced surface electric field and improved breakdown voltage

A reduced surface electric field in AlGaN/GaN high electron mobility transistor (HEMT) is investigated by employing a localized Mg-doped layer under the two-dimensional electron gas (2-DEG) channel as an electric field shaping layer. The electric field strength around the gate edge is effectively relieved and the surface electric field is distributed evenly as compared with those of HEMTs with conventional source-connected field plate and double field plate structures with the same device physical dimensions. Compared with the HEMTs with conventional source-connected field plate and double field plate, the HEMT with Mg-doped layer also shows that the breakdown location shifts from the surface of the gate edge to the bulk Mg-doped layer edge. By optimizing both the length of Mg-doped layer, L_m, and the doping concentration, a 5.5 times and 3 times the reduction in the peak electric field near the drain side gate edge is observed as compared with those of the HEMTs with source-connected field plate structure and double field plate structure, respectively. In a device with V_GS=-5 V, L_m=1.5 μm, a peak Mg doping concentration of 8× 10¹⁷ cm^-3 and a drift region length of 10 μm, the breakdown voltage is observed to increase from 560 V in a conventional device without field plate structure to over 900 V without any area overhead penalty.     

门控下InGaAs/InP单光子探测器用于符合测量的时域滤波特性研究

基于砷化镓/磷化铟雪崩光电二极管(InGaAs/InP APD)的半导体单光子探测器因工作在通信波段,且具有体积小、成本低、操作方便等优势,在实用化量子通信技术中发挥了重要作用.为尽可能避免暗计数和后脉冲对单光子探测的影响,InGaAs/InP单光子探测器广泛采用门控技术来快速触发和淬灭雪崩效应,有效门宽通常在纳秒量级.本文研究揭示了门控下单光子探测器可测量的最大符合时间宽度受限于门控脉冲的宽度,理论分析与实验结果良好拟合.该研究表明,门控下InGaAs/InP单光子探测器用于双光子符合测量具有显著的时域滤波特性,限制了其在基于双光子时间关联测量的量子信息技术中的应用.     

高电子迁移率晶体管微波损伤仿真与实验研究

针对AlGaAs/InGaAs型高电子迁移率晶体管,利用TCAD半导体仿真工具,从器件内部空间电荷密度、电场强度、电流密度和温度分布变化分析出发,研究了从栅极注入1 GHz微波信号时器件内部的损伤过程与机理。研究表明,器件的损伤过程发生在微波信号的正半周,负半周器件处于截止状态;器件内部损伤过程与机理在不同幅值的注入微波信号下是不同的。当注入微波信号幅值较低时,器件内部峰值温度出现在栅极下方靠源极侧栅极与InGaAs沟道间,由于升温时间占整个周期的比例太小,峰值温度很难达到GaAs的熔点;但器件内部雪崩击穿产生的栅极电流比小信号下栅极泄漏电流高4个量级,栅极条在如此大的电流下很容易烧毁熔断。当注入微波信号幅值较高时,在信号正半周的下降阶段,在栅极中间偏漏极下方发生二次击穿,栅极电流出现双峰现象,器件内部峰值温度转移到栅极中间偏漏极下方,峰值温度超过GaAs熔点。利用扫描电子显微镜对微波损伤的高电子迁移率晶体管器件进行表面形貌失效分析,仿真和实验结果符合较好。     

阶梯AlGaN外延新型Al_(0.25)Ga_(0.75)N/GaNHEMTs击穿特性分析

为了优化AlGaN/GaN HEMTs器件表面电场,提高击穿电压,本文首次提出了一种新型阶梯AlGaN/GaN HEMTs结构.新结构利用AlGaN/GaN异质结形成的2DEG浓度随外延AlGaN层厚度降低而减小的规律,通过减薄靠近栅边缘外延的AlGaN层,使沟道2DEG浓度分区,形成栅边缘低浓度2DEG区,低的2DEG使阶梯AlGaN交界出现新的电场峰,新电场峰的出现有效降低了栅边缘的高峰电场,优化了AlGaN/GaN HEMTs器件的表面电场分布,使器件击穿电压从传统结构的446 V,提高到新结构的640 V.为了获得与实际测试结果一致的击穿曲线,本文在GaN缓冲层中设定了一定浓度的受主型缺陷,通过仿真分析验证了国际上外延GaN缓冲层时掺入受主型离子的原因,并通过仿真分析获得了与实际测试结果一致的击穿曲线.