Temperature-dependent characteristics of 4H-SiC junction barrier Schottky diodes

The current-voltage characteristics of 4H-SiC junction barrier Schottky(JBS) diodes terminated by an offset field plate have been measured in the temperature range of 25-300 C.An experimental barrier height value of about 0.5 eV is obtained for the Ti/4H-SiC JBS diodes at room temperature.A decrease in the experimental barrier height and an increase in the ideality factor with decreasing temperature are shown.Reverse recovery testing also shows the temperature dependence of the peak recovery current density and the reverse recovery time.Finally,a discussion of reducing the reverse recovery time is presented.     

4H-SiC射频功率MESFET的自热效应分析

采用载流子速度饱和理论,建立了包含“自热效应”影响的适用于4HSiCMESFET的大信号输出IV特性解析模型,在模型中引入了温度变化的因素,提出了非恒定衬底环境温度T0的热传导模型,模拟结果与实验值一致,证明基于这种模型的理论分析符合器件测试及应用的实际情况 关键词： 4H-SiC 射频 MESFET 直流I-V特性 自热效应     

The fabrication of nickel silicide ohmic contacts to n-type 6H-silicon carbide

This paper reports that the nickel silicide ohmic contacts to n-type 6H-SiC have been fabricated. Transfer length method test patterns with NiSi/SiC and NiSi硅化镍;欧姆触点;n型碳化硅;制造;能带;带隙Project supported by the National Basic Research Program of China (Grant No~2002CB311904), the National Defense Basic Research Program of China (Grant No~51327010101) and the National Natural Science Foundation of China (Grant No~60376001).2006-09-192006-10-30This paper reports that the nickel silicide ohmic contacts to n-type 6H-SiC have been fabricated. Transfer length method test patterns with NiSi/SiC and NiSi2/SiC structure axe formed on N-wells created by N^＋ ion implantation into Si-faced p-type 6H-SiC epilayer respectively. NiSi and NiSi2 films are prepared by annealing the Ni and Si films separately deposited. A two-step annealing technology is performed for decreasing of oxidation problems occurred during high temperature processes. The specific contact resistance Pc of NiSi contact to n-type 6H-SiC as low as 1.78× 10^-6Ωcm^2 is achieved after a two-step annealing at 350 ℃for 20 min and 950℃ for 3 min in N2. And 3.84×10-6Ωcm^2 for NiSi2 contact is achieved. The result for sheet resistance Rsh of the N＋ implanted layers is about 1210Ω/□. X-ray diffraction analysis shows the formation of nickel silicide phases at the metal/n-SiC interface after thermal annealing. The surfaces of the nickel silicide after thermal annealing are analysed by scanning electron microscope.     

Ohmic contacts of 4H-SiC on ion-implantation layers

The ohmic contacts of 4H-SiC are fabricated on nitrogen ion implanted layers made by performing box-like-profile implantation three and four times. Implantation parameters such as the standard deviation σ and the projection range R_p are calculated by the Monte Carlo simulator TRIM. Ni/Cr ohmic contacts on Si-face 4H-SiC implantation layers are measured by transfer length methods (TLMs). The results show that the values of sheet resistance R_sh are 30~kΩ /□ and 4.9~kΩ/□ and the values of specific contact resistance ρ_c of ohmic contacts are 7.1× 10^-4Ω.cm² and 9.5× 10^-5Ω.cm² for the implanted layers with implantation performed three and four times respectively.     

窄缝通道对流换热与扰流柱的强化作用——关于涡轮叶片尾部冷却的研究

冷却空气高速通过叶片尾部弦向窄缝通道可对叶片尾部进行有效冷却,扰流柱的设置可提高换热系数.窄缝换热本质上就是高宽比较大的矩形通道换热,由于具有较大的散热面积早在50年代就在航空和核工业中得到较多研究,但不同作者的实验结果差别较大,在表1中列出近20多年来的一些研究结果.     

交联玻璃毛细管柱气相色谱分析香料顺反异构体

环己二甲酸二甲酯(DME),环己二甲酸二乙酯(DEE)及环已二甲酸二丁酯(DBE)是一种开发性的香料,也是合成聚酯树酯、二甲酰胺、二甲酰肼等药物的中间体。对于DME等系列化合物顺反异构体的分离,国内外报道甚少。以前气相色谱分析多采用FFAP做固定液。本工作用中国科学院     

The fabrication and characterization of 4H SiC power UMOSFETs

The fabrication of 4H-SiC vertical trench-gate metal-oxide-semiconductor field-effect transistors(UMOSFETs) is reported in this paper.The device has a 15-μm thick drift layer with 3×1015 cm-3 N-type doping concentration and a 3.1μm channel length.The measured on-state source-drain current density is 65.4 A/cm2 at Vg = 40 V and VDS = 15 V.The measured threshold voltage(Vth) is 5.5 V by linear extrapolation from the transfer characteristics.A specific on-resistance(Rsp-on) is 181 mΩ·cm2 at Vg = 40 V and a blocking voltage(BV) is 880 V(IDS = 100 μA@880V) at Vg = 0 V.     

4H-SiC肖特基二极管γ射线探测器的模型与分析

 在研究反偏压4H-SiC肖特基二极管作为g射线探测器工作机理的基础上建立了数值模型,模拟了不同偏压和辐照剂量率下探测器的暗电流、工作电流和灵敏度。模拟结果表明:探测器的灵敏度随反向偏压的增加而上升;对于Au/SiC肖特基二极管,有源区掺杂数密度为2.2×10¹⁵ cm^-3时,0 V偏压下探测器的灵敏度为13.9×10^-9 C/Gy,100 V偏压下为24.5×10^-9 C/Gy。计算结果与实验数据符合得较好。     

结终端采用JTE保护技术的4H-SiC PiN二极管模拟和研制

利用二维器件模拟软件ISE-TCAD 10.0,对结终端采用结扩展保护技术的4H-SiC PiN二极管平面器件进行反向耐压特性的模拟,并获得许多有价值的模拟数据.依据所得的模拟数据进行此种二极管器件的研制.实验测试表明,此二极管的模拟优化数据与实验测试的结果一致性较好,4H-SiC PiN二极管所测得到的反向电压达1600 V,该反向耐压数值达到理想平面结的击穿耐压90%以上.     

XRD法计算4H-SiC外延单晶中的位错密度

对用X射线衍射法计算4H-SiC外延中的位错密度方法进行了理论和实验研究。材料中的位错密度大于106 cm-2会给材料位错密度的测试会带来一定的困难。首先从理论上分析了位错密度对X射线衍射结果的影响,得出位错密度和峰宽FWHM展宽的关系。然后对4H-SiC样品进行了X射线三轴晶ω-2θ测试,采用不同晶面衍射峰,计算出样品的位错密度。分析了外延中位错产生的原因,并提出了相应的解决办法。