Tailoring band gap in GaN sheet by chemical modification and electric field: Ab initio calculations

Ab initio calculations show that the GaN monolayer (GaN-ML) in (0001) face is a planar semiconductor with an indirect band gap of 1.95 eV. The gap converts into a direct one and is enlarged by 0.81 eV when the GaN-ML is modified by H and F atoms. Furthermore, the gap can be efficiently manipulated in a range of 1.8 to 3.5 eV by applying an external electric field. Moreover, because of the spontaneous polarization, the gap is remarkably broadened by a positive electric field while it is rapidly decreased under a negative field. The chemical modification also significantly improves the stability of GaN-ML.