Effects of volumetric and potential energy change on indirect to direct bandgap transition of Ge/Sn alloy

Abstract

The germanium-tin (Ge-Sn) alloy has been considered a candidate for applications in Short Wave Infrared optical electronics, because it has the property of transforming pure germanium (Ge), typically an indirect bandgap material, into a direct bandgap material. In this paper, the effects of volumetric and potential energy changes are utilized to calculate how the band structure of the Ge-Sn alloy changes with respect to the fraction of tin (Sn). The results indicate that a transition occurs for a Sn fraction ranging from 5.81% to 8.75% with the alloy lattice-constant bowing parameter that ranges from 0.3 Å to 0.0 Å.