K、Ti掺杂Mg2Si电子结构和光学性质的第一性原理研究

采用第一性原理方法,对本征Mg₂Si以及K和Ti掺杂Mg₂Si的几何结构、电子结构和光学性质进行计算分析。计算结果表明本征Mg₂Si是带隙值为0.290 eV的间接带隙半导体材料,K掺杂Mg₂Si后,Mg₂Si为p型半导体,电子跃迁方式由间接跃迁变为直接跃迁,Ti掺杂Mg₂Si后,Mg₂Si为n型半导体,仍然是间接带隙。K、Ti掺杂后的静介电常数ε₁(0)从20.52分别增大到53.55、69.25,使得掺杂体系对电荷的束缚能力增强。掺杂后,吸收谱和光电导率均发生红移现象,这有效扩大了对可见光的吸收范围,此外可见光区的吸收系数、反射系数以及光电导率都减小,导致透射能力增强,明显改善了Mg₂Si的光学性质。

Electronic Structure and Optical Properties of K and Ti Doped Mg2Si by First-Principles Study

The geometric structure, electronic structure and optical properties of intrinsic and K, Ti doped Mg₂Si were studied by the first-principles calculation method. The calculation results indicate that the intrinsic Mg₂Si is an indirect semiconductor material with a gap of 0.290 eV. After Mg₂Si doped with K, the electronic transition mode changes from indirect transition to direct transition and the overall conduction type is p-type semiconductor. The band gap type of Mg₂Si doped with Ti has not changed, which is still an indirect band gap, and it is n-type semiconductor. The static permittivity ε₁(0) of the K and Ti doped Mg₂Si increases from 20.52 to 53.55 and 69.25, respectively, which enhances the binding ability of the doped system to charges. After doping, both the absorption spectrum and the photoconductivity have a red shift phenomenon, which effectively expands the absorption range of visible light. Besides, doping significantly decrease the absorption coefficient, reflection coefficient and photoconductivity in the visible region, which leads to an increase transmission ability, and significantly improves the optical properties of Mg₂Si.