黄铜矿型铜基硫属半导体材料的电子结构和光学性质

Electronic Structures and Optical Properties of Cu-based Semiconductors with Chalcopyrite-type Structure

采用基于赝势平面波基组的密度泛函理论方法,对具有黄铜矿结构的6种Cu XY2(X=Ga,In; Y=S,Se,Te)晶体的构型、电子结构、线性及二阶非线性光学性质进行了研究.结果表明,6种Cu XY2均为直接带隙半导体,具有相似的能带结构.当X原子相同时,随着Y原子按S→Se→Te依次改变时,体系的静态介电常数、静态折射率和静态倍频系数(d36)依次递增.在占据带中,位于价带顶附近的能带对体系倍频效应影响最为显著,该系列化合物的能带主要成分为Cu的3d轨道和Y原子价层p轨道;对于空能带,对倍频系数影响较大的是以X原子价层p轨道为主要成分的能带. 6种晶体中,Cu In Se2晶体具有较高的光电导率并对太阳光具有较好的吸收性能.综合考虑体系的双折射率和倍频效应等因素,Cu Ga S2和Cu Ga Se22种晶体在二阶非线性光学领域具有潜在的应用价值.

The density functional theory(DFT) based on the pseudo-potential plane wave basis was employed to investigate the geometries, electronic structures, linear and second-order nonlinear optical properties of the CuXY 2(X=Ga, In;Y=S, Se, Te) crystals with chalcopyrite structure. The results indicate that these compounds are semiconductors with a direct gap and have similar band structures. The static dielectric constants, the refractive indices and the second harmonic generation(SHG) coefficients( d 36 ) of these compounds increase in the sequence of S→Se→Te for the same X atom. Among the occupied bands, those states near the top of the valence band contribute mostly to the SHG effect, which are dominated by the components of Cu 3 d orbitals and the valence p orbitals of Y atom. While for the unoccupied bands, the bands mainly derived from valence p orbitals of X atoms have obvious influences on the SHG coefficient. Among these six crystals, CuInSe 2 has high photoconductivity and better absorption of sunlight. In addition, CuGaS 2 and CuGaSe 2 crystal have potential applications in the second-order nonlinear optical fields based on their birefringences and SHG strengths.