Strained Thin-Body p-MOSFET With Condensed Silicon-Germanium Source/Drain for Enhanced Drive Current Performance

Strained p-MOSFETs with silicon-germanium (SiGe) source and drain (S/D) stressors were fabricated on thin-body silicon-on-insulator (SOI) substrate using a novel local oxidation or Ge condensation technique. By directly growing SiGe on the S/D regions and followed by a local Ge condensation process, the challenges imposed on Si recess etch on thin-body SOI substrates can be alleviated. In the Ge condensation step, the Ge content in the S/D regions may also be increased. At a gate overdrive of -1 V, strained p-MOSFETs show an enhancement in the saturation drive current I_on of up to 38% over the control p-MOSFETs. This significant I_on enhancement is attributed to strain-induced band structure modification, which reduces the hole effective mass along the transport direction. The improved series resistance of the strained devices with SiGe S/D accounted for approximately one-third of the I_on enhancement.     

P—Si TFTs带间隧穿电流的建模研究

介绍了多晶硅薄膜晶体管(P-Si TFTs)中的带同隧穿(BBT)效应的产生机理,分析了BBT对P-SiTFT电流特性的影响,总结了关于P-Si TFT带间隧穿效应的研究现状,并提出建立更为完善的BBT电流模型的建模思路.     

多晶硅薄膜晶体管泄漏区带间隧穿电流的建模

讨论了带间隧穿(BBT)效应在多晶硅薄膜晶体管所有的泄漏机制中占主导地位的条件因素,说明了在高场或低温情况下,泄漏电流主要来自带间隧穿.考虑了BBT的两个产生区域--栅漏交叠处和靠近漏端的PN结耗尽区,分析了陷阱态密度以及掺杂浓度对BBT电流的影响,最后提出了一个适用于多晶硅薄膜晶体管泄漏区的带间隧穿电流模型.     

Atomistic Full-Band Design Study of InAs Band-to-Band Tunneling Field-Effect Transistors

Band-to-band tunneling field-effect transistors (BTBT FETs) are expected to exhibit a subthreshold swing (SS) better than the 60-mV/dec limit of conventional metal–oxide–semiconductor FETs at room temperature. Through atomistic modeling of a suite of realistically extended InAs p-i-n single-gate (SG) and dual-gate (DG) ultrathin-body (UTB) and gate-all-around nanowire (GAA NW) devices with a gate length of 20 nm, we demonstrate that such a reduced SS can only be achieved if the electrostatic potential under the gate contact is very well controlled. We find that GAA NWs keep an SS less than 60 mV/dec for diameters larger than 10 nm, while the bodies in DG and SG UTBs must be scaled down to 7 and 4 nm, respectively. Still, all the considered devices are characterized by an on current smaller than the ITRS requirements.      

共振隧穿二极管的开关时间特性

用HP8510(C)网络分析仪测量了AlAs/InGaAs/AlAs共振隧穿二极管(RTD)的散射参数.通过曲线拟合提取了等效电路参数,估算了RTD的开关时间.通过速度指数估算的RTD上升时间最小可达21ps.     

共振隧穿二极管的开关时间特性

用HP8510(C)网络分析仪测量了AlAs/InGaAs/AlAs共振隧穿二极管(RTD)的散射参数.通过曲线拟合提取了等效电路参数,估算了RTD的开关时间.通过速度指数估算的RTD上升时间最小可达21ps.     

共振隧穿二极管的压阻特性测试与研究

设计并搭建了检测共振隧穿二极管(RTD)压阻特性的实验系统,测试了RTD结构在不同应力状态下I-V特性曲线的漂移.实验结果表明RTD结构压阻特性的灵敏度大于1×10-8Pa-1.为了更精确地定量表达其压阻特性,研究了同一RTD结构I-V特性的一致性,得到相同环境条件下RTD电阻的最大相对漂移量小于3%,其中1%由测试仪器造成.     

纳电子器件谐振隧道二极管的研制

采用分子束外延方法在砷化镓衬底上生长了双垒单阱结构,然后用常规半导体器件工艺制成了谐振隧穿二极管(RTD),有相当好的I-V特性.对于5μm×5μm的RTD器件,在室温条件下,测得其峰谷比最大可到7.6∶1,最高振荡频率大于26GHz.     

共振隧穿二极管研究进展

简要评述共振隧穿二极管（ＲＴＤ）器件研究进展。重点探讨以下问题：为什么ＲＴＤ研究经久不衰？器件理论模型达到何等水平？器件特性、结构和材料方面有哪些关键？围绕这些问题,介绍了有关基本概念,对ＲＴＤ器件物理模型和特性近来的研究成果和前景进行了分析,并提要性地和同类的其它量子器件作了比较。     

纳电子器件谐振隧道二极管的研制

采用分子束外延方法在砷化镓衬底上生长了双垒单阱结构,然后用常规半导体器件工艺制成了谐振隧穿二极管(RTD),有相当好的I-V特性.对于5μm×5μm的RTD器件,在室温条件下,测得其峰谷比最大可到7.6∶1,最高振荡频率大于26GHz.     

共振隧穿二极管的压阻特性测试与研究

设计并搭建了检测共振隧穿二极管(RTD)压阻特性的实验系统,测试了RTD结构在不同应力状态下I-V特性曲线的漂移.实验结果表明RTD结构压阻特性的灵敏度大于1×10-8Pa-1.为了更精确地定量表达其压阻特性,研究了同一RTD结构I-V特性的一致性,得到相同环境条件下RTD电阻的最大相对漂移量小于3%,其中1%由测试仪器造成.     

Transport Mechanism of SiGe Dot MOS Tunneling Diodes

The blockage of hole transport due to excess holes In SiGe dots was observed in the MOS tunneling diodes for the first time. The five layers of self-assembled SiGe dots are separated by 74-nm Si spacers and capped with a 130-nm Si. The hole tunneling current from Pt gate electrode to p-type Si dominates the inversion current at positive gate bias and is seven orders of magnitude higher than the Al gate/oxide/p-Si device. The large work function of Pt is responsible for the hole transport current from Pt to p-Si. The incorporation of SiGe dots confines the excess holes in the valence band and forms a repulsive barrier to reduce the hole transport current from Pt to SiGe dots by 2-3 orders of magnitude in comparison with the Pt/oxide/p-Si device. This repulsive barrier also reduces the hole tunneling current from SiGe dots to Pt at negative gate bias.     

用MOCVD方法生长940nm应变多量子阱发光二极管

采用金属有机物化学气相淀积（MOCVD）方法设计并生长了应变多量子阱InGaAs/AlGaAs,并且对其进行了光致发光（PL）谱、双晶X射线衍射（DXRD）谱和电化学C－V等的测试。然后以InGaAs/AlGaAs作为有源层，以GaAs衬底作为透明衬底，p面金属电极AuBe合金作为镜面反射层，采用倒装技术制备了近红外发光二极管（LED）。在输入电流为20mA下的正向电压为1．2V左右，电致发光谱的峰值波长为938nm,10μA下的反向击穿电压为5－6V，在输入电流为50mA下得出输出功率3．5mW，对应电压为1．3V,在输入电流为300mA时得到最大输出功率为12mW。     

Drive Currents and Leakage Currents in InSb and InAs Nanowire and Carbon Nanotube Band-to-Band Tunneling FETs

The prototypical device to exploit cold carrier injection is the nanowire (NW) or carbon nanotube (CNT) band-to-band tunneling field-effect transistor. Understanding the effect of material choice and NW or CNT diameter on the drive and leakage currents is critical. A zero-order analytical approach is described for assessing and comparing the effect of different materials and diameters on the drive current, the leakage current, and the required electric fields.      

量子共振隧穿二极管的频率特性与分析

用HP8510C网络分析仪测量了AlAs/InGaAs/AlAs共振隧穿二极管的S参数,通过实测曲线拟合提取器件等效电路参数,计算出所研制器件的阻性截止频率为54GHz,并分析了影响器件工作频率的因素.     

量子共振隧穿二极管的频率特性与分析

用HP8510C网络分析仪测量了AlAs/InGaAs/AlAs共振隧穿二极管的S参数,通过实测曲线拟合提取器件等效电路参数,计算出所研制器件的阻性截止频率为54GHz,并分析了影响器件工作频率的因素.     

基于共振隧穿二极管的蔡氏电路设计研究

首次提出一种基于共振隧穿二极管的蔡氏电路.利用共振隧穿二极管(RTD)的负微分电阻特性,采用驱动点特性合成的方法,实现了蔡氏电路中的分段线性电阻,通过一组参数的选取,进而实现了蔡氏电路,并用PSpice模拟软件进行了仿真验证.相对于用传统方法实现的蔡氏电路,基于RTD的蔡氏电路具有电路结构更加简洁、便于集成的特点.     

利用空气桥技术实现InP基共振遂穿二极管器件

优化设计了InGaAs/AlAs/InP共振遂穿二极管（RTD）材料结构,并用MBE设备在（100）半绝缘InP单晶片上生长了RTD外延材料。利用电子束光刻工艺和空气桥互连技术,制作了InP基RTD器件。并在室温下测试了器件的电学特性：峰值电流密度78kA/cm2,峰谷电流比（PVCR）为7.8。利用空气桥互连技术实现该类器件,在国内尚属首次。     

平面型RTD制作过程中的两个关键工艺

采用n GaAs衬底和自对准B离子注入技术制作了平面型共振隧穿二极管,深入讨论其制作过程中几个关键问题,包括离子注入能量与剂量的选择、RTD负阻区表观正阻现象等,并系统地研究了快速合金工艺温度和时间对于制作良好欧姆接触和消除负阻区表观正阻的影响.结果表明对于所选材料,离子注入能量为130 keV,剂量为4×1013/cm2,退火温度为380℃持续60 s可得到特性较好的PRTD器件,该器件的制作为RTD的应用打下良好基础.     

Vertical Transport in GaN/AlGaN Resonant Tunneling Diodes and Superlattices

Using the transfer matrix formalism, we have theoretically studied the vertical ballistic transport in GaN/AlGaN resonant tunneling diodes (RTDs) and superlattices with a small number of periods. We have calculated the transmission probability versus the longitudinal electron energy (T–E) and the current density–voltage (J–V) characteristics. Calculations of both T–E and J–V characteristics have been performed for different Al contents in the barriers. The asymmetry effects due to the internal electric field in the barriers are discussed. Applied to the RTD structure, our calculations demonstrate: (i) the increase of the peak-to-valley ratio of the negative differential resistance (NDR) with increasing Al content in the barriers, (ii) the dependence of the J–V resonance values on the current direction, and (iii) the asymmetry of the NDR with respect to the current direction due to the huge internal electric field in the structure. In the case of multiple quantum well structure (MQWS), the calculation results confirm the same trends as in the RTD case when the Al content is varied. In spite of the fact that it is more difficult to analyze the results in the case of MQWS, the obtained calculations demonstrate the applicability of the used model and of the numerical method to study GaN/AlGaN devices based on quantum well (QW) heterostructures. Furthermore, a design of an optimized 7QW structure operating symmetrically whatever the direction of the applied voltage is presented.