A hybrid functional first-principles study on the band structure of non-strained Ge1−xSnx alloys**Project supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars of the State Education Ministry of China (Grant No. [2015]-1098), the Open Project of the State Key Laboratory of Surface Physics of Fudan University, the Natural Science Foundation of Guangdong Province of China (Grant No.

Abstract

Using hybrid-functional first-principles calculation combined with the supercell method and band unfolding technique we investigate the band structure of non-strained Ge1−xSnx alloys with various Sn concentrations. The calculations show that at the Sn concentration of ∼ 3.1 mol% the GeSn alloy presents a direct band gap. The variation of the band structure are ascribed to the weaker electro-negativity of Sn atoms and a slight charge transfer from Sn atoms to Ge atoms.