半导体材料AAl2C4(A=Zn, Cd, Hg; C=S, Se)的电子结构和光学性质

采用基于密度泛函理论的第一性原理方法, 对具有缺陷型黄铜矿结构的半导体材料A^ⅡAl₂C₄^Ⅵ(A=Zn, Cd, Hg; C =S, Se)的构型和电子结构进行研究, 并系统考察了各晶体的光学性质. 对于线性光学性质, 五种晶体在红外区和部分可见光区具有良好的透光性能, 其中HgAl₂S₄和HgAl₂Se₄晶体具有适中的双折射率. 在非线性光学性质方面, 该类晶体倍频效应较强, 理论预测得到的二阶静态倍频系数均较大(>20 pm/V). 体系的倍频效应主要来源于价带顶附近以S/Se 价p轨道为主要成分的能带向含有较多Al/Hg 价p成分的空带之间的跃迁. 通过与已商业化的AgGaC₂晶体光学性质的对比, 结果表明HgAl₂S₄和HgAl₂Se₄是一类性能优良的红外非线性光学晶体材料.

Electronic structures and optical properties of AAl2C4 (A=Zn, Cd, Hg; C=S, Se) semiconductors

First-principles density functional calculations are performed to study the geometries,the electronic and the optical properties of A^ⅡAI₂C₄^Ⅵ（A = Zn,Cd,Hg;C = S,Se） semiconductors each with a defect chalcopyrite structure.For the linear optical properties, five compounds show good transmissions of light in the IR and part of visible regions,and among them HgAl₂S₄ and HgAl₂Se₄ possess moderate birefringences.For the nonlinear optical properties,the strong second harmonic generation（SHG） response can be expected for these crystals,and the large static SHG coefficients（> 20 pm/V） are predicted in this work.The SHG response of A^ⅡAl₂C₄^Ⅵsemiconductors can be attributed to the transitions from the bands near the top of valence band which are derived from S/Se p states to the unoccupied bands that are contributed by p states of A1 and Hg atoms.By comparing with the optical properties of the commercialized AgGaC₂ crystals,our results indicate that HgAl₂S₄ and HgAl₂Se₄ compounds are good candidates for the second-order nonlinear optical crystals in the IR region.