Physical properties of group 14 semiconductor alloys in orthorhombic phase

Abstract

The structural properties, electronic band structures, mechanical anisotropy, and the stability of Si, SiGe, Ge, GeSn, and Sn in the Cmca phase are comprehensively investigated in this paper. Si, Ge, and Sn, when in the Cmca phase, are dynamically, thermodynamically, and mechanically stable. Firstly, two novel semiconductor materials with direct bandgap are proposed in this paper. When Ge atoms and Sn atoms are combined into compounds with the Cmca phase at a stoichiometric ratio of 1:1, the bandgap is 0.48 eV, and Sn in the Cmca phase is also a direct bandgap semiconductor material with a bandgap of 0.41 eV. In addition, the mechanical anisotropy of Si, SiGe, Ge, GeSn, and Sn in the Cmca phase and SiGe and GeSn in the F4¯3m phase is systematically studied, investigating the bulk modulus, shear modulus, Young's modulus, and Poisson's ratio. Young's modulus of SiGe and GeSn in the Cmca phase exhibits the largest mechanical anisotropy in (111) and (001) planes. In the F4¯3m phase, the mechanical anisotropy is smaller than that of SiGe and GeSn, except for in the (111) plane, due to the (111) plane of SiGe and GeSn, in the F4¯3m phase, being mechanically isotropic.