K掺杂正交相Ca_2Si电子结构和光学性质的第一性原理计算

First-principles calculation of electronic structure and optical properties of K-doped orthorhombic Ca_2Si

采用第一性原理的平面波赝势方法和广义梯度近似(GGA),对K掺杂正交相Ca2Si前后的电子结构和光学性质进行比较分析。计算表明,掺K后正交相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0.4318 eV,光学带隙变宽;掺杂K后价带主要是Si的3p态,Ca的3d、4s态以及K的3p、4s态的贡献。并利用计算的能带结构和态密度分析了K掺杂正交相Ca2Si前后的复介电函数、能量损失函数、反射光谱及吸收光谱,结果显示掺K增强了材料对太阳光谱中红外波段的能量利用。研究结果说明掺杂是改变材料电子结构和光电性能的有效手段,为Ca2Si材料光电性能的开发与应用提供了理论依据。

The electronic structure and optical properties of K-doped orthorhombic Ca2 Si were calculated and analyzed by using first-principles plane wave pseudopotential method with generalized gradient approximation(GGA).The calculated results show that K-doped Ca2Si is a direct semiconductor that move towards higher energy and the band gap is 0.4318 eV,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 3d,4s and K 3p,4s.Furthermore,the dielectric function,the loss function,the reflectivity and the absorption of Ca2Si and K-doped Ca2Si were analyzed in terms of the calculated band structure and densities of states.It can enhance the absorption of infrared range of the sun spectrum for K-doped Ca2Si.The calculation results reveal that the electronic structure and optical properties of Ca2Si can be modulated effectively by doping.They also provide theoretical data for the design and application of optolectronic materials of Ca2Si.