Research on atomic structure analysis of silicon carbide semiconductor single crystal and interface of oxide film

碳化硅（SiC）器件没有呈现出理论上预期的性能。这是由于SiO_2/SiC界面缺陷降低了材料的电性能。在本研究中，我们试图通过计算机模拟来解决这些问题。为了将计算机模拟应用于真实的界面结构，在SiC表面构建非晶SiO_2（a-SiO_2）结构是一个重要的研究课题。采用第一性原理分子动力学方法，建立了4 H-SiC（0001）晶层上a-SiO_2的693原子平板模型。计算是用地球模拟器上的VASP程序进行的。采用加热淬火法制备了a-SiO2/SiC界面结构。在4000 K温度下，除两个界面层、SiO_2层的表面Si和终止表面Si的H外，在固定SiC层的条件下，SiO_2层熔化加热界面结构2 ps。界面 关于我们 在不改变约束条件的情况下，将结构冷却到3500 K。在去除H和释放表面Si之后，在3500 K温度下对界面结构进行2 ps的连续退火。在自由界面SiC层由两层扩展到四层后，将界面结构淬火到室温。计算了SiO_2层的径向分布函数（RDF）。Si和O之间的最近邻原子间距离变为0.165 nm。Si和Si之间的最近邻原子间距离变为0.305 nm。当这个距离转换成Si-O-Si键角时，它变成135度。该角度与石英玻璃中的Si-O-Si键角一致。0和0之间的最近邻原子间距离变为0.268 nm，并转换为109度的O-Si-O键角。这个角几乎等于硅原子为中心的四面体中的键角109.5度。通过对加热淬火法的模拟，证实了可以生成a-SiO_2层。少

Silicon carbide (SiC) devices don't present the theoretically expected performance. This is considered to be attributed to the SiO_2/SiC interface defects that degrade the electrical performance of them. In this study, we tried to solve these problems by the computer simulation. For the application of computer simulation to the realistic interface structures, it is important to construct the structure of amorphous SiO_2 (a-SiO_2) on SiC. The slab model using 693 atoms for a-SiO_2 on a 4H-SiC (0001) crystal layer was constructed by using first-principles molecular dynamics (MD) method. The calculations have been performed by the VASP code on the Earth-Simulator. The heating and quenching method was carried out to make an a-SiO_2/SiC interface structure. The SiO_2 layers melted heating the interfacial structure by 2 ps in the temperature of 4000K on the condition of fixing SiC layers except 2 interfacial layers, surface Si of SiO_2 layers and H that terminate surface Si. The interfacial … More structure has been cooled down to the temperature of 3500K without changing the restriction. After the removal of H and release of surface Si, the interfacial structure was continuously annealed for 2 ps at the temperature of 3500K. After free interfacial SiC layers had been expanded from two layers to four layers, the interfacial structure was quenched to the room temperature. The radial distribution function (RDF) of the SiO_2 layers was calculated. The nearest neighbor interatomic distance between Si and O became 0.165 nm. The nearest neighbor interatomic distance between Si and Si became 0.305 nm. When this distance is converted into Si-O-Si bond angle, it becomes 135 deg. This angle agrees well with Si-O-Si bond angle in the silica glass. The nearest neighbor interatomic distance between 0 and 0 became 0.268 nm, and is converted into O-Si-O bond angle of 109 deg. This angle is almost equal to bond angle of 109.5 deg in Si-atom-centered tetrahedra. It was confirmed to be able to generate the a-SiO_2 layer with the simulation of the heating and quenching method. Less