The first principle study of the electronic structure of SixGe(1−x) alloy films

First principles calculation based on density functional theory (DFT) with the generalized gradient approximation (GGA) are carried out to investigate the electronic band structures of SixGe(1−x) alloys nanofilms. The calculation results show that the band gaps of (100), (110) and (111) surfaces SixGe(1−x) alloy films with different thickness first increase with the increase of Si content, then flatten out, and finally decrease. At the same time, the transformation of direct band gap and indirect band gap occurs when the thickness of films and Si content of the three surface SixGe(1−x) alloy films changes to a certain critical condition. It will be a good way to obtain direct-gap band emission in SixGe(1−x) alloys materials.