Al掺杂4H-SiC第一性原理计算及二次离子质谱分析

本文采用基于密度泛函理论的第一性原理计算,使用CASTEP软件建立了4H-SiC重掺杂模型,对通过激光辐照固态Al膜制备的p型重掺杂4H-SiC薄膜的晶体结构和电子结构进行了计算分析,研究获得不同浓度Al掺杂4H-SiC的能带结构和态密度.结果表明,随着Al原子掺杂浓度的增大,辐照样品禁带宽度随之减小,费米能级进入价带,体现出p型半导体的特征.结合二次离子质谱测试分析,得到Al掺杂浓度随辐照层深度的变化规律,Al掺杂浓度在30 nm范围内较为均匀,约为1×10^20cm^-3.证明KrF准分子激光可以实现4H-SiC之Al原子重掺杂,随着深度的增加,激光能量密度逐渐降低,4H-SiC内Al原子掺杂浓度相应降低.验证了激光辐照Al膜掺杂所制备4H-SiC样品的p型半导体特征,得到了Al掺杂浓度随激光辐照深度的变化规律.

First-principles study on Al doped 4H-SiC

In this paper,by using first principles calculation based on density functional theory,4H-SiC heavily doped model was established using CASTEP software.The crystal structure and electronic structure of p-type Al heavily-doped 4H-SiC prepared by laser irradiation of coated Al film have been calculated and studied.The band structure and densities of state corresponding to various doping concentration of Al were analyzed.The results show that the bandgap width decreases with the increase of Al atom doping concentration and the Fermi level enters the valence band,which reflects the characteristics of p-type semiconductor the laser doped 4H-SiC.Combined with the analysis of secondary ion mass spectrometry,the variation of Al doping concentration with depth was obtained.It was found that the uniform doping concentration of Al which is approximately 1×10^20 cm^-3 is in the depth range of 30 nm.It is proved that the Kr F excimer laser can achieve heavy doping of Al atoms in 4H-SiC.With the increase of depth,the laser energy density decreases gradually,and the doping concentration of Al atoms in 4H-SiC decreases.The p-type semiconductor characteristics of4H-SiC samples prepared by laser irradiation Al film doping were verified,and the variation of Al doping concentration with laser irradiation depth was obtained.