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

碳化硅（SiC）器件没有表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。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实际界面结构，在碳化硅上构建非晶SiO_2 （a-SiO_2）结构是十分重要的。采用第一性原理分子动力学（MD）方法，在4H-SiC（0001）晶体层上建立了693个a- sio_2的板状模型。计算已由VASP代码在地球模拟器上执行。采用加热淬火法制备了a-SiO_2/SiC界面结构。除2个界面层、SiO_2层的表面Si和终止表面Si的H外，其余SiO_2层在固定SiC层的条件下，在4000K温度下加热2 ps使界面结构熔化。在不改变限制条件的情况下，将界面结构冷却到3500K。去除H，释放表面Si后，在3500K温度下连续退火2 ps。自由界面SiC层由两层扩展到四层后，将界面结构淬火至室温。计算了SiO_2层的径向分布函数。Si和O之间最近邻的原子间距离为0.165 nm。Si和Si之间最近邻的原子间距离为0.305 nm。当这个距离转换为Si-O-Si键角时，它变成135°，这个角度与硅玻璃中的Si-O-Si键角非常吻合。在0和0之间的最近邻原子间距离变为0.268 nm，转换成O-Si-O键角为109°，这个角几乎等于硅原子中心四面体的109.5°键角。通过对加热淬火法的模拟，证实了a-SiO_2层的生成是可行的。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