The effect of vacancy defects on the conductive properties of SiGe

Abstract

Electronic band structures of defective silicon–germanium (SiGe) were described using ab initio calculations, and the influences of vacancy defects on the conductive properties of SiGe were studied. The analysis of formation energies of the defects indicates that a Si atom is easier to lose than a Ge one to form a single vacancy (SV) defect, and double vacancy (DV) defects might be more frequently found than two adjacent SV defects in SiGe. A vacancy could be formed more easily in Ge-rich than Si-rich SiGe. The band structures of SiGe compounds are affected conspicuously by defects, making most of the SixGe8−x compounds with SVs show a trend to become to p-type, and almost all of the SixGe8−x compounds with DVs turn to n-type. The p-type property might come from the vacancies with +2 charged state, and n-type property from the vacancies with −2 charged state.