短沟道SOI BJMOSFET的阈值电压

提出了一种适用于短沟道SOI BJMOSFET阈值电压特性分析的电荷分享物理模型,详细讨论了短沟道SOI BJMOSFET背界面处于积累、反型以及全耗尽三种状态时的阈值电压,并利用Math-ematica软件进行数值模拟得到阚值电压的特性曲线.通过理论分析和计算机模拟,证明短沟道SOI BJMOSFET阈值电压的可控性很强,更适用于现代ULSI低压低功耗的要求.     

单壁碳纳米管作沟道的场效应晶体管输运特性理论研究

为研究以单壁碳纳米管(CNT)作沟道的场效应晶体管(FET)的输运特性,采用非平衡格林函数(NEGF)理论,构建了CNTFET的电子输运模型,该方法摒弃粗糙的连续体模型,可实现CNTFET输运性质与手性指数的直接对接。以(17,0)锯齿型管为例,数值计算了CNTFET输出特性、转移特性、跨导、亚阈值摆幅、开关态电流比等电学特性;在等效栅氧化层厚度相同的情况下,对比了采用不同栅介质材料时上述电学特性在数值上的差异,发现随栅介质介电常数的增加,漏感应势垒降低效应变得显著,这不但导致开态时从源注入到漏的电子浓度增加、电流增大,也导致关态电流增大,开关态的电流比减少。研究还发现在通常的栅源和漏源电压下,沟道中出现热电子。     

短沟道n-MOSFET亚阈值电流模拟计算分析

本文基于亚阈值电流和表面势模型的基础上,采用商用器件模拟软件,建立了短沟道n-MOSFET的结构和物理模型,对器件的亚阈值电流进行了2-D数值模拟。计算了不同沟道掺杂浓度、氧化层厚度以及沟道长度对器件亚阈值电流的影响,并对模拟结果进行了系统的理论分析,数值模拟结果和解析模型能够在亚阈值区很好的吻合。     

亚100nm NMOSFET的沟道反型层量子化效应研究

介绍了CMOS技术发展到亚100nm所面临的挑战。针对尺寸量子化效应。建立了NMOSFET的反型层电子量子化模型,分析了反型层量子化效应对NMOSFET器件参数包括有效栅氧厚度、阈值电压等的影响。得出结论,反型层量子化效应致使反型层电子分布偏离表面。造成有效栅氧厚度的增加,阈值电压的波动达到约10％。     

4H-SiC隐埋沟道MOSFET亚阈特性研究

在推导一个等效沟道厚度模型的基础上,对SiC隐埋沟道MOSFET亚阈特性进行了研究.首先利用泊松方程的解对等效沟道厚度的计算式进行了推导,计算结果表明,在N D/N-A≤43的情况下,等效沟道厚度与栅压和沟道深度无关,亚阈区峰值电势随栅压线性变化,推出了一个简化的亚阈电流表达式,并在计算中计入了界面态的影响.该表达式可用来对沟道载流子浓度进行提取.     

氢流量对纳米SiC薄膜微结构和光学特性的影响

采用螺旋波等离子体增强化学气相沉积技术进行了氢化纳米晶态SiC薄膜的沉积,研究了氢流量对其微结构和光学特性的影响.结果显示,随着氢气流量的增大,薄膜的沉积速率先增大后减小,所生长薄膜晶化度显著提高.在较低氢流量条件下,薄膜光学带隙的大小由氢的刻蚀与悬键终止作用共同控制,并呈先减小后增大的趋势.在高氢流量条件下,强的氢刻蚀使薄膜具有较高的晶化度,虽然薄膜中整体氢含量有所下降,但存在于纳米碳化硅晶粒表面键合氢的相对密度持续增大,纳米碳化硅晶粒数量的增加和晶粒尺寸的减小所导致的量子限制效应使薄膜的光学带隙继续展宽.     

Surface channel MESFETs on hydrogenated diamond

Metal–semiconductor field effect transistors (MESFETs) based on hydrogen terminated diamond were fabricated according to different layouts. Aluminum gates were used on single crystal and low-roughness polycrystalline diamond substrates while gold was used for ohmic contacts. Hydrogen terminated layers were deeply investigated by means of Hall bars and transfer length structures. Room temperature Hall and field effect mobility values in excess of 100 cm2 V?1 s?1 were measured on commercial and single crystal epitaxial growth (100) plates by using the same hydrogenation process. Hydrogen induced two-dimensional hole gas resulted in sheet resistances essentially stable and repeatable depending on the substrate quality. Self-aligned 400 nm gate length FETs on single crystal substrates showed current density and transconductance values>100 mA mm?1 and >40 mS mm?1, respectively. Devices with gate length LG=200 nm showed fMax=26.4 GHz and fT=13.2 GHz whereas those fabricated on polycrystalline diamond, with the same gate geometry, exceeded fMax=23 GHz and fT=7 GHz. This work focused on the optimization of a self-aligned gate structure with respect to the fixed drain-to-source structure with which we observed higher frequency values; the new structure resulted in improvement of DC characteristics, better impedance matching and a reduction in the fMax/fT ratio.     

Microwave characteristics of SiC artificial crystal

Design and simulation of a new type of stealthy material are presented, including theory, methodology, and results/discussion. This material consists of a three-dimensional periodic lattice of SiC ceramic dielectric rods with SiO₂ as matrix. Transmission, reflection and absorption coefficients of the material are calculated. Proper parameters which meet the stealthy requirements are obtained from the numerical calculation. It's found that when conductivity is equal to 1 × 10^0.4 Sm⁻¹, the maximum absorption loss is got at 6 GHz. The main advantages of this material are light-weight, high temperature stability, and high impedance matching the free space.     

Degradation of ion implanted GaAs MESFETs

Ion-implanted Si-doped GaAs MESFETs with 1μm and 5μm gate lengths have been subjected to DC life testing at temperatures of 220°C and 250°C for 4000 and 2250 h, respectively. Two failure mechanisms have been identified:

• 1 Diffusion of platinum from the gate contact into the n-GaAs channel.
• 2 An increase of deep-level trapping, specifically of EL2 (E_a=0.8 eV), in the channel region.

     

Dynamical characteristics of wave-excited channel flow

This paper is part of a study on the receptivity characteristics of the shear flow in a channel whose walls are subjected to a wave-like excitation. The small amplitude forced wavy wall motion is characterised by a wave number vectorλ ₁,λ ₂ and a frequencyω _g . The basic flow in the problem is a superposition of the Poiseuille flow and a periodic component that corresponds to the wave excitation of the wall. The aim of the study is to examine the susceptibility of this flow to transition. The problem is approached through studying the stability characteristics of the basic flow with respect to small disturbances. The theoretical framework for this purpose is Floquet theory. The solution procedure for solving the eigenvalue problem is the spectral collocation method. Preliminary results showing the influence of the amplitude and the wave number of the wall excitation on the stability boundary of the flow are presented.     

High‐temperature device performance and thermal characteristics of GaAs MESFETs on CVD diamond substrates

The temperature degradation and high‐temperature characteristics of GaAs FETs on CVD diamond heat sinks were investigated by modeling the high‐temperature electrical characteristics for GaAs MESFETs and by experimentally measuring the elevated‐temperature degradation. The bias region for the Zero‐Temperature Coefficient (ZTC) was determined. The thermal characteristics were determined by infra‐red microscopy and the results were correlated with a finite element analysis calculation of GaAs FET thermal distribution. Copyright © 2000 John Wiley & Sons, Ltd.     

Cracking characteristics of reinforced steel fiber concrete beams under short- and long-term loadings

In this paper, an analytical method for the prediction of maximum crack width in reinforced steel fiber concrete (SFC) beams under short-term loading is first presented. The method accounts for the enhanced cracking strength, restraint against crack growth, and reduced tensile steel strains due to the presence of steel fibers. Based on a correlation analysis, a semiempirical formula for the long-term crack widths in reinforced SFC beams under sustained loads is also proposed. Tests were carried out on 10 beams to investigate the effect of steel fiber content on the cracking characteristics in both the short- and long-term. The results indicated that the use of steel fibers greatly reduced the maximum crack widths in reinforced concrete beams. Good agreement was generally obtained between the analytical predictions and test results.     

Energy characteristics of SiC(0001)-intercalated hydrogen-graphene system

The properties of a SiC(0001)-H-C(graphene) system have been studied by considering a cluster comprising two C atoms of graphene, three Si atoms of the SiC substrate, and two or three channeled H atoms. Calculations of the electron structure and bond energies are performed using the Harrison bonding orbital method. The influence of channeled H atoms on the system energy are analyzed using two schemes. It is shown that the scheme (A → B) involving two H atoms is energetically unfavorable, while the scheme (A → C) with three H atoms provides a gain in the energy.     

微纳米SiC/环氧树脂复合材料的界面和非线性电导特性

以微米和纳米SiC为填料,制备了不同填料配比的微纳米SiC/环氧树脂(EP)复合材料。测试了微纳米SiC/EP复合材料的玻璃化转变温度、室温介电谱和直流电导特性。分析了填料与基体之间的界面对玻璃化转变温度、介电谱及直流电导特性的影响。实验结果表明,在微米和纳米SiC填料的共同掺杂下,随着纳米SiC填料含量的增加,微纳米SiC/EP复合材料的玻璃化转变温度先降低后升高。在相同频率下,微纳米SiC/EP复合材料具有更低的相对介电常数和低频损耗峰幅值。与EP相比,微纳米SiC/EP复合材料具备显著的非线性电导特性。与微米SiC/EP复合材料相比,微纳米SiC/EP复合材料具有更高的非线性指数和阈值电场强度。微纳米SiC/EP复合材料的非线性电导特性与SiC颗粒和EP基体之间的界面区密切相关。