A CAD oriented quasi-analytical large-signal drain current model for 4H-SiC MESFETs

This paper reports that a 4H-SiC MESFET （Metal Semiconductor Field Effect Transistor） large signal drain current model based on physical expressions has been developed to be used in CAD tools. The form of drain current model is based on semi-empirical MESFET model, and all parameters in this model are determined by physical parameters of 4H-SiC MESFET. The verification of the present model embedded in CAD tools is made, which shows a good agreement with measured data of large signal DC I-V characteristics, PAE （power added efficiency）, output power and gain.

Advanced SPICE-Modeling of 4H-SiC MESFETs

A modified drain source current suitable for simulation program with integrated circuit emphasis （SPICE） simulations of SiC MESFETS is presented in this paper. Accurate modeling of SiC MESFET is achieved by introducing three parameters in Triquint＇s own model （TOM）. The model, which is single piece and continuously differentiable, is verified by measured direct current （DC） I-V curves and scattering parameters （up to 20 GHz）.

Physical simulations and experimental results of 4H-SiC MESFETs on high purity semi-insulating substrates

In this paper we report on DC and RF simulations and experimental results of 4H-SiC metal semiconductor field effect transistors （MESFETs） on high purity semi-insulating substrates. DC and small-signal measurements are compared with simulations. We design our device process to fabricate n-channel 4H-SiC MESFETs with 100 #m gate periphery. At 30 V drain voltage, the maximum current density is 440 mA/mm and the maximum transconductance is 33 mS/mm. For the continuous wave （CW） at a frequency of 2 GHz, the maximum output power density is measured to be 6.6 W/mm, with a gain of 12 dB and power-added efficiency of 33.7%. The cut-off frequency （fT） and the maximum frequency （fmax） are 9 GHz and 24.9 GHz respectively. The simulation results of fT and fmax are 11.4 GHz and 38.6 GHz respectively.

Electrothermal simulation of the self-heating effects in 4H-SiC MESFETs

A thermal model of 4H-SiC MESFET is developed based on the temperature dependences of material parameters and three-region I - V model. The static current characteristics of 4H-SiC MESFET have been obtained with the consideration of the self-heating effect on related parameters including electron mobility, saturation velocity and thermal conductivity. High voltage performances are analysed using equivalent thermal conductivity model. Using the physicalbased simulations, we studied the dependence of self-heating temperature on the thickness and doping of substrate. The obtained results can be used for optimization of the thermal design of the SiC-based high-power field effect transistors.

真空慢退火工艺对4H-SiC核辐射探测器性能的影响

制备了一种肖特基二极管结构的4H-SiC辐射探测器.在真空环境下,用不同的温度对欧姆电极进行慢退火处理,达到良好的欧姆接触.对其反向I-V特性和能量分辨率进行测试对比,欧姆电极在800℃条件下性能最好,在全耗尽状态下能量分辨率为1.36%,耐压测试运行稳定, 200 V偏压下漏电流仅有463 pA.与其他退火温度相比,该工艺下的4H-SiC探测器运行稳定,具有漏电流低、能量分辨率高的优势.

基于4H-SiC的开槽四梁式压阻式加速度计设计及仿真研究

基于4H-SiC设计了一种开槽四梁式的压阻式加速度计,通过分析开槽位置、开槽大小对传感器灵敏度及固有频率的影响确定了开槽的相关参数,并对该结构采用有限元方法进行了热-力耦合仿真,确定了该结构在不同温度场下施加不同载荷时的理论电压输出。研究结果表明:该结构相较于传统双端四梁结构输出灵敏度提升51.4%,固有频率仅下降14.2%,在ANSYS 600℃的稳态温度场环境下,传感器输入载荷与输出电压成线性关系,理论满量程输出为39.71 mV。

4H-SiC晶片热导率的激光拉曼光谱研究

在本研究中,使用激光激发的激光拉曼光谱研究了4H-SiC晶片从低温(80 K)到室温(290 K)的热导率。在整个测量过程中,激光既作为拉曼光谱的激发源又作为热源,通过激光加热提高了晶片表面的局部温度。同样,拉曼峰的位置会随着晶片温度的升高而向高频侧偏移,通过分析拉曼光谱位置的偏移和局部温度升高的关系得到了4H-SiC晶片的热导率。结果表明,4H-SiC晶片的热导率在低温情况下随温度升高而升高,此时K∝T 3,当热导率的值达到最大后随着温度的升高而降低,此时K∝T-1,这归因于声子-声子间相互作用和声子缺陷散射的作用。

4H-SiC光导开关性能的仿真研究

碳化硅光导开关是相关领域的研究热点,但是文献中对4H-SiC光导开关的理论研究仍然以集总元件模型为主,仅能给出定性结果,典型文献中瞬态条件下的实验数据还没有定量的理论解释。文章使用SilvacoTCAD软件中的器件-电路混合模式,结合自编的载流子迁移率接口程序,对4H-SiC光导开关的光学电学特性进行模拟仿真。单脉冲响应的仿真结果表明,器件在瞬态条件下的峰值光电流随光能的变化与文献中的实验数据相符合,表明所用模型和参数具有合理性。对影响单脉冲响应的主要因素,包括脉冲能量、脉冲宽度、碳化硅厚度,进行了计算和分析。同时,针对两种碳化硅厚度的器件,进行了多脉冲串响应的计算和分析。文章得到的结果和结论对碳化硅光导开关的进一步研究具有较好的参考价值。

Improved dual-channel 4H-SiC MESFETs with high doped n-type surface layers and step-gate structure

An improved dual-channel 4H-SiC MESFET with high doped n-type surface layer and step-gate structure is proposed, and the static and dynamic electrical performances are analyzed.A high doped n-type surface layer is applied to obtain a low source parasitic series resistance, while the step-gate structure is utilized to reduce the gate capacitance by the elimination of the depletion layer extension near the gate edge, thereby improving the RF characteristics and still maintaining a high breakdown voltage and a large drain current in comparison with the published SiC MESFETs with a dual-channel layer.Detailed numerical simulations demonstrate that the gate-to-drain capacitance, the gate-to-source capacitance, and the source parasitic series resistance of the proposed structure are about 4%, 7%, and 18% smaller than those of the dual-channel structure, which is responsible for 1.4 and 6 GHz improvements in the cut-off frequency and the maximum oscillation frequency.

Improved empirical DC I-V model for 4H-SiC MESFETs

A novel empirical large signal direct current （DC）Ⅰ-Ⅴ model is presented considering the high saturation voltage, high pinch-off voltage, and wide operational range of drain voltage for 4H-SiC MESFETs. A comparison of the presented model with Statz, Materka, Curtice-Cubic, and recently reported 4H-SiC MESFET large signal Ⅰ-Ⅴ models is made through the Levenberg-Marquardt method for fitting in nonlinear regression. The results show that the new model has the advantages of high accuracy, easily making initial value and robustness over other models. The more accurate results are obtained by the improved channel modulation and saturation voltage coefficient when the device is operated in the sub-threshold and near pinch-off region. In addition the new model can be implemented to CAD tools directly, using for design of 4H-SiC MESFET based RF＆MW circuit, particularly MMIC （microwave monolithic integrate circuit）.

4H-SiC射频功率MESFET大信号直流I-V特性解析模型

根据 4H - Si C高饱和电子漂移速度和常温下杂质不完全离化的特点 ,对适用于 Si和 Ga As MESFET的直流I- V特性理论进行了分析与修正 .采用高场下载流子速度饱和理论 ,以双曲正切函数作为表征 I- V特性的函数关系 ,建立了室温条件下 4H - Si C射频功率 MESFET直流 I- V特性的准解析模型 ,适于描述短沟道微波段 4H- Si CMESFET的大信号非线性特性 ,计算结果与实验数据有很好的一致性 .同时与 MEDICI模拟器的模拟结果也进行了比较 .

基于实验与物理分析的4H-SiC射频功率MESFET大信号非线性精确电容模型

采用电荷控制理论和载流子速度饱和理论的物理分析方法 ,并结合 Statz、Angelov等经验模型的描述方法 ,提出了常温下针对 4 H- Si C射频功率 MESFET的大信号非线性电容模型 .此模型在低漏源偏压区对栅源电容 Cgs强非线性的描述优于 Statz、Angelov等经验模型 ,计算量也远低于基于器件物理特性的数值模型 。

4H-SiC功率MESFET直流I-V特性解析模型

提出了一种改进的4H-SiC MESFET大信号直流解析模型。该模型基于栅极下面电荷的二维分布进行分析,在考虑电场相关迁移率、速度饱和及沟道内电荷堆积的基础上,计入沟道长度调制效应,建立基于物理的沟道长度调制效应模型。计算结果表明,计入沟道长度调制效应后的直流模型在饱和区与实测的I-V特性较为吻合。

基于国产单晶衬底的150 mm 4H-SiC同质外延技术进展

高阻断电压、大功率密度、高转化效率是电力电子器件技术持续追求的目标,基于4H-SiC优异的材料特性,在电力电子器件应用方面具有广阔的发展前景。围绕SiC MOSFET器件对外延材料的需求,介绍了国内外主流的SiC外延设备及国产SiC衬底的发展,并重点介绍了宽禁带半导体电力电子器件国家重点实验室在国产150 mm(6英寸)SiC衬底上的高速外延技术进展。通过关键技术攻关,实现了150 mm SiC外延材料表面缺陷密度≤0.5 cm-2,BPD缺陷密度≤0.1 cm-2,片内掺杂浓度不均匀性≤5%,片内厚度不均匀性≤1%。基于自主外延材料,实现了650~1200 V SiC MOSFET产品商业化以及6.5~15 kV高压SiC MOSFET器件的产品定型。

(NH_4)_2S_x溶液改善GaAs MESFETs击穿特性的机理研究

使用 (NH4) 2 Sx 溶液对GaAsMESFETs进行处理。处理后 ,器件各栅偏压下的源漏饱和电流降低了 ,栅漏击穿电压有了显著提高。我们认为负电荷表面态影响着栅边缘的电场 ,负电荷表面态密度的增大会提高器件的击穿电压 ,这就是 (NH4) 2 Sx

国产4H-SiC SI衬底MESFET外延生长及器件研制

以国产衬底实现SiC加工工艺链为目标,采用国产4H-SiC半绝缘衬底材料外延得到4H-SiC MESFET结构材料。外延片XRD半宽43.2 arcs,方块电阻121点均匀性18.39%,随后制备出的具有直流特性的4H-SiC MESFET器件管芯,器件总栅宽250μm,饱和电流密度680 mA/mm,跨导约为20 mS/mm,在20 V下的栅漏截止漏电为10μA,2 mA下栅漏击穿电压为80 V。比例占总数的70%以上。初步实现从衬底到外延,进而实现器件的完整工艺链,为进一步的工艺循环打下良好基础。

4H-SiC MESFET高频小信号特性的模拟与分析

建立了4H SiCMESFETs的模型,运用二维器件模拟软件MEDICI对4H SiCMESFETs的高频小信号特性进行了研究.利用正弦稳态分析的方法对4H SiCMESFETs的高频小信号特性进行了模拟,模拟结果与实验数值比较表明在特征频率fT以内得到了较为满意的结果.分析了不同的栅长、栅漏间距、不同的沟道掺杂以及温度变化对SiCMESFET特征频率fT的影响.

4H-SiC MESFET的反应离子刻蚀和牺牲氧化工艺研究

对于栅挖槽的4H-SiCMESFET,栅肖特基接触的界面经过反应离子刻蚀,界面特性对于肖特基特性和器件性能至关重要。反应离子刻蚀的SiC表面平滑度不是很好,刻蚀损伤严重。选择合适的RIE刻蚀条件减小刻蚀对半导体表面的损伤;利用牺牲氧化改善刻蚀后的表面形貌,进一步减小表面的刻蚀损伤。工艺优化后栅的肖特基特性有了明显改善,理想因子接近于1。制成的4H-SiCMESFET直流夹断特性良好,饱和电流密度达到350mAmm。

4H-SiC MESFET结构外延生长技术

利用热壁式CVD技术生长4H-SiC MESFET结构外延材料,TMA和氮气分别用作p型和n型掺杂源.外延层厚度使用SEM进行表征,SIMS及汞探针C-V用作外延层掺杂浓度测试.通过优化生长参数,成功生长出高质量的MESFET结构外延材料并获得陡峭的过渡掺杂曲线,并给出了部分器件测试结果.

4H-SiC MESFET器件的制备与性能

在半绝缘4H-SiC衬底上成功制备出MESFET器件,并完成直流特性测试和交流小信号特性测试工作.共制备出3种结构尺寸的MESFET器件,其栅长栅宽分别为0.5μm/80μm,0.7μm/80μm和2μm/2mm,其中0.5μm/80/μm的MESFET器件的漏极电流密度最高,频率特性最好.在漏源电压Vds=10V时,它的漏极电流Ids约为14mA,电流密度为175mA/mm,最大跨导为25mS/mm,fT=3.5GHz,fmax=7GHz.