Electronic and Optical Properties of Rutile GeₓSn₁₋ₓO₂ Alloys for Power Electronics Devices

Rutile GeₓSn₁₋ₓO₂ alloys have recently sparked research interest as candidate ultra-wide band gap materials for energy-efficient power electronics devices due to their predicted ambipolar dopability, as well as high carrier mobility and high thermal conductivity. Experiments show that these alloys have carrier mobilities that are insensitive to alloy disorder at a low Ge content, and can be grown in thin films across a wide range of compositions. In this study, we investigate the electronic band structure of rutile GeₓSn₁₋ₓO₂ alloys using the GW approximation of many-body perturbation theory and calculate the optical absorption spectra by solving the Bethe-Salpeter equation. While rutile GeO₂ and SnO₂ have fundamental band gaps that are dipole-forbidden, we explore how symmetry breaking from local alloy disorder leads to these transitions becoming dipole-allowed and quantify its effect on the optical properties of the alloy. Our results reveal the electronic and optical features of GeₓSn₁₋ₓO₂ that provide insight into its potential as an ultra-wide band gap semiconductor for power electronics and deep-UV applications.