Electronic structure and optical properties of Ge96−xSnx (0≤x≤50): A first-principles study

In this work, the electronic structure and optical properties of Ge96−xSnx (0 ≤ x ≤ 50) alloys are calculated from first-principles based on the density functional theory (DFT). Generalized gradient approximation with Hubbard correction parameter U (GGA + U) was used for exchange-correlation potential. The calculation results present that the lattice constant increases, while the band gap width decreases with increasing Sn content. The Ge96−xSnx alloys feature transition to direct band gap when the Sn content is above 10 at.%. The static values of the real part of dielectric function and the refractive index increase with increasing Sn content. The peak values and the fine-structure positions of the dielectric function strongly depend on the Sn content. The absorption coefficient and optical conductivity spectrum increase their intensity and feature red-shifts with increasing Sn content in Ge96−xSnx.