K掺杂立方相Ca2Si电子结构及光学性能的研究

基于第一性原理的密度泛函理论赝势平面波方法,采用广义梯度近似（GGA）对掺K的立方相Ca2Si的电子结构和光学性能,包括能带结构、态密度、介电函数、折射率、反射率、吸收系数、光电导率及能量损失函数进行理论计算,结果表明,掺K后立方相Ca2Si的能带向高能方向发生了偏移,形成直接带隙的P型半导体,禁带宽度为0.6230eV,光学带隙变宽,价带主要是Si的3p、Ca的4s、3d以及K的3p、4s态的贡献;静态介电函数ε1（0）=14.4;折射率n0=3.8;吸收系数最大峰值为3.47×105cm-1。通过掺杂调制材料电子结构和光电性能,为Ca2Si材料光电性能的开发与应用提供了理论依据。

Study on the Electronic Structure and Optical Properties of K-doped Cubic Ca2Si

The electronic structure and optical properties of K-doped cubic Ca2Si are calculated and analyzed by using first-principles plane wave pseudopotential method with GGA, including the band structure, the density of states, the dielectric function, the refractive index, the reflectivity, the absorption, the conductivity and the loss function. The calculated results show that K-doped Ca2Si is a direct band gap semiconductor that moves towards higher energy and the band gap is 0.6230eV, the sample is p-type semiconductor and its optical bandgap is broadened. The valence bands of K-doped Ca2Si are mainly composed of Si 3p, Ca 4s, 3d and K 3p, 4s. The static dielectric function ε1（0） is 14.4, the refractive index n0 is 3.8, the biggest peak of absorption coefficient is 3.47×105cm-1. The electronic structure and optical properties of Ca2Si can be modulated effectively by doping. The results offer theoretical data for the design and application of optolectronic materials of Ca2Si.