Impact of surface point defects on the electronic and optical properties of GeSi bulk materials

GeSi compounds are promising for next-generation optoelectronic applications because of their tuneable bandgap and high carrier mobility, but surface point defects can significantly alter their electronic and optical properties. Using first-principles density functional theory calculations, the effects of vacancies, interstitials, and antisite defects in Ge_0.8Si_0.2 are systematically examined in this study. The results reveal that vacancies and interstitials introduce mid-gap states, narrowing the bandgap and enhancing absorption, whereas antisite defects cause subtle performance change. These findings provide critical insights into defect engineering strategies for optimizing GeSi-based devices.