Model and analysis of drain induced barrier lowering effect for 4H-SiC metal semiconductor field effect transistor

Based on an analytical solution of the two-dimensional Poisson equation in the subthreshold region, this paper investigates the behavior of DIBL （drain induced barrier lowering） effect for short channel 4H-SiC metal semiconductor field effect transistors （MESFETs）. An accurate analytical model of threshold voltage shift for the asymmetric short channel 4H-SiC MESFET is presented and thus verified. According to the presented model, it analyses the threshold voltage for short channel device on the L/a （channel length/channel depth） ratio, drain applied voltage VDS and channel doping concentration ND, thus providing a good basis for the design and modelling of short channel 4H-SiC MESFETs device.

Modeling of the drain-induced barrier lowering effect and optimization for a dual-channel 4H silicon carbide metal semiconductor field effect transistor

A new analytical model to describe the drain-induced barrier lowering （DIBL） effect has been obtained by solving the two-dimensional （2D） Poisson＇s equation for the dual-channel 4H-SiC MESFET （DCFET）. Using this analytical model, we calculate the threshold voltage shift and the sub-threshold slope factor of the DCFET, which characterize the DIBL effect. The results show that they are significantly dependent on the drain bias, gate length as well as the thickness and doping concentration of the two channel layers. Based on this analytical model, the structure parameters of the DCFET have been optimized in order to suppress the DIBL effect and improve the performance.

GaN HEMT源漏通道区电阻的自热和准饱和效应模型

GaN HEMT在栅极与源极和漏极之间存在一段通道区域,在等效电路模型中通常等效为一电阻,称为源漏通道区电阻R_(D,S)。准确构建GaN HEMT R_(D,S)模型,对于分析GaN HEMT直流和射频特性,构建GaN HEMT大信号模型具有十分重要的意义。本研究给出考虑自热和准饱和效应的R_(D,S)模型。首先由源漏通道区温度T_(CH)与耗散功率P_(diss)的关系,推导出非线性自热效应模型。进一步基于准饱和效应和Trofimenkoff模型,给出源漏通道区电子漂移速度与电场强度的关系表达式,构建非线性R_(D,S)模型。在环境温度Tamb=300~500 K时,源漏通道区二维电子气2DEG面密度n_(S,acc)(T_(CH))和迁移率μ_(acc)(T_(CH))随T_(CH)的升高而下降,这导致低偏置条件下的源漏通道区电阻R_(D0,S0)随T_(CH)呈非线性增长。将本研究和文献报道的R_(D,S)模型与TCAD(Technology Computer Aided Design)仿真数据进行对比,结果显示:本研究与文献报道的漏通道区电阻RD模型的平均相对误差分别为0.32%和1.78%,均方根误差(RMSE)分别为0.039和0.20Ω;RS模型的平均相对误差分别为0.76%和1.73%,RMSE分别为0.023和0.047Ω。与文献报道的实验数据进行对比,结果显示:本研究与文献RD模型的平均相对误差分别为0.91%和1.59%,RMSE分别为0.012和0.015Ω;RS平均相对误差分别为1.22%和2.77%,RMSE分别为0.0015和0.0034Ω。本研究提出的R_(D,S)模型具有更低的平均相对误差和均方根误差,能够更加准确地表征GaN HEMT线性工作区R_(D,S)随漏源电流I_(DS)的变化。可将本模型用于器件的设计优化,也可作为Spice模型用于电路仿真。

考虑粉土温度效应与排水状态的CPTu计算模型

温度变化对土体性质和行为的潜在影响已成为许多岩土工程设计和应用的重要组成部分。针对粉土中孔压静力触探试验(piezocone penetration test,简称CPTu)的温度效应及部分排水状态,提出了基于小孔扩张理论的计算模型和分析方法。采用一种能够表征粉土强度温度效应的本构模型,给出了完全不排水和排水条件下的解析解;以Bourke粉土为例,分析了温度对扩张压力的影响,揭示了扩张压力随温度升高而减小的规律。采用一种线性映射方法给出了部分排水条件下的小孔扩张半解析解,并基于物理模型试验的结果得出了排水状态与温度的相关关系,建立了考虑粉土温度效应与排水状态的CPTu计算模型。研究了不同贯入速率下温度对CPTu测试结果的影响,结果表明,温度升高导致锥尖阻力与锥肩孔压减小,且变化幅度随超固结比的增加而增大,通过试验结果与计算模型预测结果的对比验证了模型的可靠性。

渐变沟道全耗尽SOI MOSFET漏致势垒降低效应研究

目的 集SOI MOSFET(绝缘衬底上的硅金属氧化物半导体场效应晶体管)器件结构与渐变沟道的优点于一体,提出渐变沟道全耗尽SOI MOSFET器件结构,以提高MOSFET器件的微观物理性能。方法 分别列出沟道不同掺杂浓度的2个区域的泊松方程并求解,建立阈值电压模型。依据计算结果,详细分析沟道高掺杂区的掺杂浓度和掺杂长度、栅氧化层的介电常数、硅膜厚度等物理参数对漏致势垒降低(DIBL)效应的影响。结果 DIBL随沟道高掺杂区的掺杂浓度的增大而变小,随掺杂长度的减小而变小,随栅氧化层的介电常数的增大而变小,随硅层厚度减薄而变小。结论 渐变掺杂沟道结构能够有效抑制器件的DIBL。该研究结果不仅对器件的理论研究有一定的意义,而且对器件的设计提供了一定的参考价值。

适用于SiC MOSFET的漏源电压积分自适应快速短路保护电路研究

SiC MOSFET因其高击穿电压、高开关速度、低导通损耗等性能优势而被广泛应用于各类电力电子变换器中。然而,由于其短路耐受时间仅为2~7μs,且随母线电压升高而缩短,快速可靠的短路保护电路已成为其推广应用的关键技术之一。为应对不同母线电压下的Si C MOSFET短路故障,文中提出一种基于漏源电压积分的自适应快速短路保护方法(drain-sourcevoltageintegration-basedadaptivefast short-circuit protection method,DSVI-AFSCPM),研究所提出的DSVI-AFSCPM在硬开关短路(hardswitchingfault,HSF)和负载短路(fault under load,FUL)条件下的保护性能,进而研究不同母线电压对DSVI-AFSCPM的作用机理。同时,探究Si CMOSFET工作温度对其响应速度的影响。最后,搭建实验平台,对所提出的DSVI-AFSCPM在发生硬开关短路和负载短路时不同母线电压、不同工作温度下的保护性能进行实验测试。实验结果表明,所提出的DSVI-AFSCPM在不同母线电压下具有良好的保护速度自适应性,即母线电压越高,短路保护速度越快,并且其响应速度受Si CMOSFET工作温度影响较小,两种短路工况下工作温度从25℃变化到125℃,短路保护时间变化不超过90 ns。因此,该文为Si CMOSFET在不同母线电压下的可靠使用提供一定技术支撑。

运用“朋辈效应”缓解农村青年人才流失问题的路径研究

青年是我国改革、发展的重要动力,是最有力量的“强国一代”,对我国政治、经济、社会等多个领域都产生重要的贡献。在新时代背景下,参与乡村振兴是作为“强国一代”的青年应当承担和肩负的重要责任。2024年中央一号文件再次提出“壮大乡村人才队伍”,通过实施乡村振兴人才支持计划,加强对乡村本土人才的培养,全面提高农民的综合素质。解决农村地区青年人才流失问题刻不容缓。

A two-dimensional analytical model for channel potential and threshold voltage of short channel dual material gate lightly doped drain MOSFET

An analytical model for the channel potential and the threshold voltage of the short channel dual-material-gate lightly doped drain （DMG-LDD） metal-oxide-semiconductor field-effect transistor （MOSFET） is presented using the parabolic approximation method. The proposed model takes into account the effects of the LDD region length, the LDD region doping, the lengths of the gate materials and their respective work functions, along with all the major geometrical parameters of the MOSFET. The impact of the LDD region length, the LDD region doping, and the channel length on the channel potential is studied in detail. Furthermore, the threshold voltage of the device is calculated using the minimum middle channel potential, and the result obtained is compared with the DMG MOSFET threshold voltage to show the improvement in the threshold voltage roll-off. It is shown that the DMG-LDD MOSFET structure alleviates the problem of short channel effects （SCEs） and the drain induced barrier lowering （DIBL） more efficiently. The proposed model is verified by comparing the theoretical results with the simulated data obtained by using the commercially available ATLASTM 2D device simulator.

考虑指数渗流的砂井地基弹黏塑性固结分析

为深入探究饱和黏土地区砂井地基的固结机制,在Barron自由应变假定下,引入考虑时间效应的统一硬化(unified hardening,UH)模型描述土骨架的变形非线性关系,同时引入指数渗流方程代替Darcy定律,并考虑渗透系数变化及涂抹效应的影响,研究了土体非线性、施工扰动及外载荷等因素对砂井地基非线性固结过程的影响规律。结果表明:由于土体的黏滞效应,在加载前期,砂井地基不排水边界附近孔压出现升高现象,且考虑非Darcy渗流时上述现象更加明显,砂井地基固结速率也愈加缓慢。此外,涂抹区渗透系数的减小显著降低了砂井地基整体孔压消散速率,而外载荷的增大却加快了地基的固结进程。

Enhanced radiation-induced narrow channel effects in 0.13-μm PDSOI nMOSFETs with shallow trench isolation

Total ionizing dose responses of different transistor geometries after being irradiated by ^（60）Co γ-rays, in 0.13-μm partially-depleted silicon-on-insulator（PD SOI） technology are investigated. The negative threshold voltage shift in an n-type metal-oxide semiconductor field effect transistor（nMOSFET） is inversely proportional to the channel width due to radiation-induced charges trapped in trench oxide, which is called the radiation-induced narrow channel effect（RINCE）.The analysis based on a charge sharing model and three-dimensional technology computer aided design（TCAD） simulations demonstrate that phenomenon. The radiation-induced leakage currents under different drain biases are also discussed in detail.

Numerical study of self-heating effects of small-size MOSFETs fabricated on silicon-on-aluminum nitride substrate

Compared with bulk-silicon technology, silicon-on-insulator (SOI) technology possesses many advan-tages but it is inevitable that the buried silicon dioxide layer also thermally insulates the metal – oxide – silicon field-effect transistors (MOSFETs) from the bulk due to the low thermal conductivity. One of the alternative insulator to replace the buried oxide layer is aluminum nitride (AlN), which has a thermal conductivity that is about 200 times higher than that of SiO2 (320 W·m ? 1·K? 1 versus 1.4 W·m? 1·K? 1). To investigate the self-heating effects of small-size MOSFETs fabricated on silicon-on-aluminum nitride (SOAN) substrate, a two-dimensional numerical analysis is performed by using a device simulator called MEDICI run on a Solaris workstation to simulate the electri-cal characteristics and temperature distribution by comparing with those of bulk and standard SOI MOSFETs. Our study suggests that AlN is a suitable alternative to silicon dioxide as a buried dielectric in SOI and expands the appli-cations of SOI to high temperature conditions.

四妙散合萆薢渗湿汤加减联合提脓祛腐外治法治疗臁疮湿热下注证临床研究

目的:观察四妙散合萆薢渗湿汤加减联合提脓祛腐外治法治疗臁疮湿热下注证临床疗效。方法:选取2021年7月至2022年12月在河南中医药大学第一附属医院就诊的臁疮患者80例为研究对象,采用随机数字表法分为对照组和观察组,每组各40例,对照组采用提脓祛腐外治法治疗,观察组在对照组治疗基础上加四妙散合萆薢渗湿汤加减治疗,4周后比较两组患者临床疗效、中医证候评分、肉芽组织覆盖率、疼痛视觉模拟评分、血清炎症因子水平等。结果:对照组有效率为70.00%,观察组有效率为95.00%,两组有效率比较,差异有统计学意义(P<0.05)。两组患者治疗后主症、次症总分均低于治疗前,差异有统计学意义(P<0.05),且组间比较,差异有统计学意义(P<0.05)。两组患者治疗后各时间点肉芽组织覆盖率均升高,与治疗前比较,差异有统计学意义(P<0.05),且组间比较,差异有统计学意义(P<0.05)。两组患者治疗后各时间点VAS评分均降低,与治疗前比较,差异有统计学意义(P<0.05),且组间比较,差异有统计学意义(P<0.05)。两组臁疮患者治疗后超敏C反应蛋白(hypersensitive C-reactive protein,hs-CRP)、白细胞介素-6(interleukin-6,IL-6)、IL-1β水平均降低,与治疗前比较,差异有统计学意义(P<0.05),且组间比较,差异有统计学意义(P<0.05)。结论:四妙散合萆薢渗湿汤加减联合提脓祛腐外治法可有效改善臁疮湿热下注证患者临床症状,加快创面恢复,减轻炎症反应程度。

Temperature and drain bias dependence of single event transient in 25-nm FinFET technology

In this paper, we investigate the temperature and drain bias dependency of single event transient （SET） in 25-nm fin field-effect-transistor （FinFET） technology in a temperature range of 0-135 ℃ and supply voltage range of 0.4 V- 1.6 V. Technology computer-aided design （TCAD） three-dimensional simulation results show that the drain current pulse duration increases from 0.6 ns to 3.4 ns when the temperature increases from 0 to 135 ℃. The charge collected increases from 45.5 ℃ to 436.9 fC and the voltage pulse width decreases from 0.54 ns to 0.18 ns when supply voltage increases from 0.4 V to 1.6 V. Furthermore, simulation results and the mechanism of temperature and bias dependency are discussed.

Improved power simulation of AlGaN/GaN HEMT at class-AB operation via an RF drain–source current correction method

A new modified Angelov current–voltage characteristic model equation is proposed to improve the drain–source current（Ids） simulation of an Al Ga N/Ga N-based（gallium nitride） high electron mobility transistor（Al Ga N/Ga N-based HEMT） at high power operation. Since an accurate radio frequency（RF） current simulation is critical for a correct power simulation of the device, in this paper we propose a method of Al Ga N/Ga N high electron mobility transistor（HEMT）nonlinear large-signal model extraction with a supplemental modeling of RF drain–source current as a function of RF input power. The improved results of simulated output power, gain, and power added efficiency（PAE） at class-AB quiescent bias of Vgs =-3.5 V, Vds= 30 V with a frequency of 9.6 GHz are presented.

脓毒症胃肠功能障碍采用半夏泻心汤的疗效观察分析

目的 观察脓毒症胃肠功能障碍采用半夏泻心汤的疗效,确定半夏泻心汤临床应用价值。方法 选择2021年8月-2022年8月在本院接受脓毒症胃肠功能障碍治疗的70例患者作为本次研究对象,将患者入院编号进行统计,将单数患者划入研究组中,将偶数患者划入对照组中,每组各35例。对照组患者采用常规治疗,研究组患者在常规治疗基础上实施半夏泻心汤治疗,比较两组脓毒症胃肠功能障碍患者APACHEⅡ、SOFA、中医症候积分、腹内压、肠鸣音、血清二胺氧化酶、血清D-乳酸、PCT、CRP差值、胃肠功能障碍评分以及临床治疗效果。结果 治疗后,研究组患者APACHEⅡ、SOFA、中医症候积分低于对照组,差异有统计学意义(P<0.05)。治疗后,研究组患者腹内压与肠鸣音情况于优对照组,差异有统计学意义(P<0.05)。治疗后,研究组患者血清二胺氧化酶、血清D-乳酸、PCT、CRP差值低于对照组,差异有统计学意义(P<0.05)。治疗后,研究组患者胃肠功能障碍评分低于对照组,差异有统计学意义(P<0.05)。治疗后,研究组临床治疗效果高于对照组,差异有统计学意义(P<0.05)。结论 在临床脓毒症胃肠功能障碍治疗中,半夏泻心汤临床应用效果确切,能够切实改善患者胃肠功能,加快促进患者临床病症转归,缩短患者住院时间。

Double-gate-all-around tunnel field-effect transistor

In this work, a double-gate-all-around tunneling field-effect transistor is proposed. The performance of the novel device is studied by numerical simulation. The results show that with a thinner body and an additional core gate, the novel device achieves a steeper subthreshold slope, less susceptibility to the short channel effect, higher on-state current, and larger on/off current ratio than the traditional gate-all-around tunneling field-effect transistor. The excellent performance makes the proposed structure more attractive to further dimension scaling.

GaSb p-channel metal-oxide-semiconductor field-effect transistor and its temperature dependent characteristics

GaSb p-channel metal-oxide-semiconductor field-effect transistors （MOSFETs） with an atomic layer deposited Al2O3 gate dielectric and a self-aligned Si-implanted source/drain are experimentally demonstrated. Temperature dependent electrical characteristics are investigated. Different electrical behaviors are observed in two temperature regions, and the un- derlying mechanisms are discussed. It is found that the reverse-bias pn junction leakage of the drain/substrate is the main component of the off-state drain leakage current, which is generation-current dominated in the low temperature regions and is diffusion-current dominated in the high temperature regions. Methods to further reduce the off-state drain leakage current are given.

考虑温度和初始孔压非均布的竖井地基固结解

针对目前竖井地基热固结理论的不足,建立了基于轴对称下竖井地基固结计算模型,采用解析解法推导了考虑温度和初始孔压非均布影响的竖井地基固结一般解;给出了初始孔压呈梯形分布、矩形分布、正三角形分布和倒三角形分布下的超静孔压和固结度的计算表达式。根据所得解析解,编制计算程序,通过参数敏感性分析对竖井地基的固结特性进行研究。结果表明:在温度不变时,初始孔压的分布形式对固结特性有较大影响;初始孔压呈矩形和正三角形分布时,温度越高,超静孔压的消散速率越快;竖井地基底部的孔压值在固结过程中总是最大的,当初始孔压呈倒三角和梯形分布时,随着温度的升高,地基底部孔压值呈现由小变大的特点。

UTBB SOI MOSFETs短沟道效应抑制技术

随着栅极长度、硅膜厚度以及埋氧层厚度的减小,MOS器件短沟道效应变得越来越严峻。本文首先给出了决定全耗尽绝缘体上硅短沟道效应的三种机制;然后从接地层、埋层工程、沟道工程、源漏工程、侧墙工程和栅工程等六种工程技术方面讨论了为抑制短沟道效应而引入的不同UTBB SOI MOSFETs结构,分析了这些结构能够有效抑制短沟道效应(如漏致势垒降低、亚阈值摆幅、关态泄露电流、开态电流等)的机理;而后基于这六种技术,对近年来在UTBB SOI MOSFETs短沟道效应抑制方面所做的工作进行了总结;最后对未来技术的发展进行了展望。

腹腔镜胆总管探查后免T管与T管引流术治疗胆总管结石的临床疗效分析

目的比较腹腔镜胆总管探查后免T管法(胆总管一期缝合及经胆囊管取石)与T管引流法治疗胆总管结石的临床疗效及安全性。方法回顾性分析芜湖市第二人民医院2018年3月至2021年8月期间收治的28例行免T管腹腔镜胆总管探查的胆总管结石患者的临床资料,随机选取同期行T管引流法腹腔镜胆总管探查术的胆总管结石的患者28例作为对照组,比较两组术中一般情况如手术成功率(有无中转开腹及术后结石残余),手术时间,术中出血量;以及两组患者术后相关指标如术后首次肛门排气时间,术后住院时间,术后各时间节点疼痛视觉模拟法评分(VAS)及术后并发症等指标的差异。结果免T管组与T管引流组相比,在平均手术时间、术后首次肛门排气时间、术后住院时间以及术后各时间点VAS评分均有明显优势,P<0.05;而在术后总体并发症发生率方面,两组相比较无明显差异。结论腹腔镜胆总管探查后免T管法与T管引流法均是安全、可靠的术式,免T管法可以加快患者术后康复,在熟练掌握腹腔镜技术及严格把握手术适应证的前提下值得临床推广。