First-principles calculations to investigate Band structure and effective masses of direct bandgap hexagonal GeSn alloys

It is well known that hexagonal Ge has a direct bandgap and exhibits excellent light emission. The structure and electrical characteristics of hex-GeSn alloys are investigated using an ab initio computation and the PBEsol-meta-GGA-mBJ function. In all alloys, the direct bandgap is observed. Due to the high radius of the Sn atom, when Sn content increases, the bandgap decreases and lattice parameters expand. Their spin-orbit, crystal field splitting and effective mass of electron and hole were also determined, indicating that the direct bandgap of hex-GeSn alloys has significant application in optoelectronic.