SiC欧姆接触特性

通过离子注入外延层实现高浓度掺杂和直接采用高掺杂外延层两种方法分别制备了4H-SiC欧姆接触,对应退火条件分别为(950℃,Ar,30 min)和(1000℃,N2,2 min).采用传输线法测试得到的比接触电阻分别为1.359×10-5Ω.cm2和3.44×10-6Ω.cm2.二次离子质谱分析表明,高温退火过程中镍硅化合物和TiC的形成有利于欧姆接触特性.     

用Cr/Au/Ni/Au制备n-GaN欧姆接触

为了获得n-GaN的低接触电阻的欧姆接触,采用Cr/Au/Ni/Au金属化系统与n—GaN形成欧姆接触,并对其不同温度下的接触电阻率进行了测试分析.室温下Cr/Au/Ni/Au的接触电阻率为0.32mΩ·m2。随着温度的升高,接触电阻率略有增加,在300℃时接触电阻率为0.65mΩ·cm2,因此此欧姆接触适合在高温下使用.     

多晶硅纳米膜欧姆接触特性的研究

采用LPCVD和PECVD方法制作单层金属铝的多晶硅纳米膜欧姆接触,并用X射线对其表征,说明铝膜具有多晶结构.在温度为450℃的条件下,分别对5 min、20 min和40 min的不同退火时间进行测试,得到在20 min时Ⅰ-Ⅴ特性曲线表现出好的欧姆接触,构成线性关系,方块电阻达1 kΩ,与接触电阻率相吻合,传输长度变到15 μm,接触电阻为30 Ω,说明电流的传导能力变强.     

表面氢化降低SiC/金属接触间界面态密度的机理

研究了SiC表面氢化降低界面态密度的机理。采用缓慢氧化、稀释的HF刻蚀、沸水浸泡的表面氢化处理方法,降低SiC表面态密度。该方法用于SiC器件的表面处理,在100℃以下制备了理想因子为1.20~1.25的6H-SiC肖特基二极管,其欧姆接触比接触电阻为(5~7)×10-3Ω· cm2。表面氢化处理的优点在于避免了欧姆接触所需的800~1 200℃的高温合金,降低了工艺难度,改善了肖特基结的电学特性。     

薄层轻掺杂N-GaAs半导体欧姆接触研究

利用Ni/Ge/Au/Ni/Au和Pd/In两种金属结构成功地对体硅掺杂N-GaAs半导体(Nd=10¹⁸cm^-3)和离子注入N-GaAs半导体(dose=8×10¹²cm²,注入有源区深度(d=0.2μm)制成低阻欧姆接触。并对实验结果和接触机理进行了讨论。所得合金接触的接触电阻率分别为10^-6Ωcm²(10¹⁸cm^-3掺杂),和10^-3Ωcm^-2(8×10¹²cm²注入)数量级并具有长期的稳定性。接触制备方法和GaAs工艺相适。     

Al金属多晶硅纳米膜欧姆接触的制作

利用低压化学气相淀积法（LPCVD）在表面有热氧化二氧化硅的（100）硅衬底上生长80nm厚多晶硅纳米膜,并对其界面进行表征.制作出单层Al金属的欧姆接触样品,在不同退火温度条件下对样片的电阻进行测量.结果表明,退火使欧姆接触的电阻率降低,接触电阻率可达到2.41×10-3Ω.cm2.     

GaN HEMT外延材料欧姆接触的研究

研究了Ti/Al/Ni/Au多层金属与GaNHEMT结构外延片的欧姆接触,发现接触特性与金属蒸发后的退火温度密切相关.在氮气氛中880℃条件下快速热退火30s,获得了为6.94×10-7·cm2的比接触电阻.光学显微镜观察表明,在这个条件下退火后金属层具有良好的表面形貌.     

AlGaN/GaN HEMT研制及特性分析

以蓝宝石为衬底研制出栅长1μm AlGaN/GaN HEMT．在室温下,测试该器件显示出良好的输出特性和肖特基伏安特性,最大跨导160mS/mm,栅压1V下饱和电流720mA/mm,击穿电压大于50V．分析了几个关键工艺对器件特性的影响,指出较大的欧姆接触电阻(3.19Ω·mm)限制了器件性能进一步提高,需提高肖特基接触的势垒高度．     

808nm半导体激光器接触电阻的最佳工艺

欧姆接触的好坏，对高功率半导体激光器至关重要。降低接触电阻，有利于降低阈值，提高效率和延长寿命。为此，我们做了大量的实验，找到了降低欧姆接触电阻的最佳工艺条件，获得了小于0.06欧姆的最低电阻。     

808nm半导体激光器接触电阻的最佳工艺

欧姆接触的好坏，对高功率半导体激光器至关重要降低接触电阻，有利于降低阈值，提高效率和延长寿命。为此，我们做了大量的实验，找到了降低欧姆接触电阻的最佳工艺条件，获得了小于０．０６区域的最低电阻。     

Effect of silver growth temperature on the contacts between Ag and ZnO thin films

Highly c-axis oriented ZnO thin films were deposited on Si substrates by the pulsed laser deposition (PLD) method. At different growth temperatures, 200 nm silver films as the contact metal were deposited on the ZnO thin films. The growth temperatures have great influence on the crystal quality of Ag films. Current-voltage characteristics were measured at room temperature. The Schottky contacts between Ag and ZnO thin films were successfully obtained when silver electrodes were deposited at 150°C and 200°C. Ohmic contacts were formed while the growth temperatures were lower than 150°C or higher than 200°C. After analysis, the forming of Ag/ZnO Schottky contacts was shown to be dependent on the appearance of the p-type inversion layer at the interface between Ag and ZnO layers.     

基于大电流密度下欧姆接触退化的新方法

在大电流密度下对欧姆接触结果进行考核,对传统的传输线法测量接触电阻率的结构与方法进行了改进,充分考虑到了半导体材料受到的影响,可达到只对接触区域老化而不破坏其他区域.工艺制备中实现台面刻蚀斜坡效果,并采取多次SiO_2淀积多次光刻技术,有效降低了引线电极断裂的概率.通过大电流密度老化结果显示:接触电阻率早期快速失效,且随电流密度及老化时间的增加而退化加剧.对样品老化前后进行能谱分析得知:接触层中的Al是一种较低的抗电迁移能力的金属,由于电迁移被冲击出来从而破坏了良好接触层.改进后的结构对测量大电流密度下的欧姆接触是一种好方法.     

4H-SiC trench gate MOSFETs with field plate termination

Field plate(FP)-terminated 4H-SiC trench gate MOSFETs are demonstrated in this work.N+/P?/N?/N+multiple epitaxial layers were grown on 3-inch N+type 4H-SiC substrate by chemical vapor deposition(CVD),and then the 4H-SiC trench gate MOSFETs were fabricated based on the standard trench transistor fabrication.Current-voltage measurements in forward and reverse bias have been performed on different devices with and without FP protections.It is found that more than 60%of the devices protected with FP termination are able to block 850 V.The measurements also show that the devices have the small leakage currents 0.15 nA at 600 V and 2.5 nA at 800 V,respectively.The experimental results also were compared with the simulated results,which show good agreement with each other in the trend.The limited performance of the devices is mainly because of the damage induced on the trench sidewalls from the etching process and the quality of the SiO2 films.Therefore,the 4H-SiC trench gate MOSFETs are expected to be optimized by reducing the etching damage and growing high-quality SiO2 dielectric films.     

Reduction of deep level defects in unintentionally doped 4H-SiC homo-epilayers by ion implantation

In order to reduce deep level defects, the theory and process design of 4H-SiC homoepitaxial layer implanted by carbon ion are studied. With the Monte Carlo simulator TRIM, the ion implantation range, location of peak concentration and longitudinal straggling of carbon are calculated. The process for improving deep energy level in undoped 4H-SiC homoepitaxial layer by three times carbon ion-implantation is proposed, including implantation energy, dose, the SiO2 resist mask, annealing temperature, annealing time and annealing protection. The deep energy level in 4H-SiC material can be significantly improved by implantation of carbon atoms into a shallow surface layer. The damage of crystal lattice can be repaired well, and the carbon ions are effectively activated after 1 600 ℃ annealing, meanwhile, deep level defects are decreased.     

Analytical model for capacitance-voltage characteristics of ion-implanted 4H silicon carbide Schottky barrier diodes

In order to undertake theory analysis in the application area of switching,frequency and power devices,an analytical model for capacitance-voltage (C-V) characteristics of ion-implanted 4H silicon carb...     

Ni/4H-SiC SBD电离辐照探测器的实验研究

研制了Ni/4H-SiC肖特基二极管电离辐照探测器,并采用不同的辐照源进行了测试。实验结果表明,对于低能电子和γ射线辐照,该探测器都有比较灵敏的电流响应。经过1 Mrad(Si)的γ射线辐照后,探测器的信号电流没有明显退化;分别经过1 Mrad(Si)的γ射线和100 Mrad(Si)的1 MeV电子辐照后,0 V和-30 V辐照偏压下的探测器的暗电流仅有较轻微的退化。说明了该文研制的探测器具有暗电流低、灵敏度高和抗辐射容限高等优点,可以在强辐射环境中长时间应用。     

含苹果颗粒果汁通电加热速度与优化模型

对含苹果颗粒苹果汁通电加热过程中的加热速度、加热时间、电导率和温度等变化规律进行了研究,结果表明:含苹果颗粒苹果汁的电导率随着温度升高、颗粒尺寸减小和颗粒质量分数降低而按线性增大;随着颗粒尺寸减小和颗粒质量分数降低,通电加热时间缩短,加热速度增大;颗粒形状对电导率、通电加热时间和温度变化影响不显著。为探究各因素对加热速度影响及因素间的交互作用,采用正交多项式回归设计试验建立通电加热速度数学模型,得出各因素对通电加热速度影响按从大到小的顺序依次为颗粒尺寸、颗粒质量分数、颗粒形状。当苹果立方体颗粒边长为0.5cm、颗粒质量分数为20%时,固液混合物料通电加热时间最短,为348s,通电加热速度最大;优化出通电加热速度与影响因素关系的三元多项式回归数学模型,对预测分析含苹果颗粒果汁通电加热温度变化规律和通电加热速度有实际意义。     

4H-SiC MESFET高频小信号特性的模拟与分析

建立了4H-SiC MESFETs的模型,运用二维器件模拟软件MEDICI对4H-SiC MESFETs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-SiC MESFETs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f_T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SiC MESFET特征频率f_T的影响．