First-principles study of electronic structure and optical and mechanical properties of SiGeSn alloy

The unique optical properties of SiGeSn alloy contribute to its remarkable potential in Si photonics applications. In this paper, the first-principles plane-wave super-soft pseudopotential generalized gradient approximation +U (GGA+ U) method was used to investigate the 96-atom supercell structure of SixGe96-x-ySny (0 <= x = y <= 9) alloy. The lattice constants, electronic structure, mechanical properties and optical properties of the alloy were discussed. Results show that the lattice constant increases, the bandgap width decreases, resist external forces is weakened, and the bulk is easily deformed of SixGe96-x-ySny alloy with the increase in silicon-tin content. The dielectric function, refractive index, and photoconductivity of SixGe96-x-ySny alloy vary with the concentration of silicon and tin. The increase in silicon-tin concentration leads to an increase in infrared (IR) light absorption, resulting in a red shift. The effective mass of the electron decreases, the effective mass of the hole increases in the alloy, and the ratio D gradually increases, indicating that the carrier life is prolonged with the increase in Si and Sn concentrations.