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。这被认为是由于SiO_2/SiC界面缺陷降低了它们的电性能所致。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到真实的界面结构中，在碳化硅上构建非晶态SiO_2(a-SiO_2)结构是非常重要的。用第一性原理分子动力学(MD)方法建立了4H-SiC(0001)晶层上a-SiO_2的693个原子的板条模型。这些计算是在地球模拟器上用VASP程序完成的。采用加热淬火的方法制备了a-SiO_2/SiC界面结构。除2个界面层、SiO_2层的表面硅和终止表面硅的H外，其余SiO_2层在4000K的温度下熔融加热2ps的界面结构。界面…更多的结构在不改变限制条件的情况下冷却到3500K的温度。在脱氢和表面硅释放后，界面结构在3500K下连续退火2ps。自由界面碳化硅从两层扩展到四层后，界面结构被淬火到室温。计算了SiO_2层的径向分布函数。Si和O之间的最近邻原子间距为0.165 nm。Si和Si之间的最近邻原子间距为0.305 nm。当这个距离换算成Si-O-Si键角时，它变成135度。这一角度与石英玻璃中的Si-O-Si键角吻合较好。0和0之间的最近邻原子间距为0.268 nm，并转化为109deg的O-Si-O键角。这个角度几乎等于以硅原子为中心的四面体中109.5度的键角。通过对加热方式和淬火方式的模拟，证实了可以形成a-SiO_2层。较少

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