First-principles study of band gap engineering of ZnO by alloying with LiGaO2 for ultraviolet applications

Structure and electronic properties of Zn(1-x)(LiGa)(0.5x)O are examined by first-principles methods. The calculations indicate that stable forms of Zn(1−x)(LiGa)(0.5x)O alloys may have different space groups with their parent materials. Our results show the orthorhombic lattices with Pm, Pmn21, and P1 structures have lower formation energies than the wurtzite lattices at a given (LiGa)0.5 composition. The band-gap energies of Zn(1−x)(LiGa)(0.5x)O in the wurtzite and orthorhombic structure are nearly identical and all compounds have direct band gaps. The gap widens as the (LiGa)0.5 concentration increases due to a weaker hybridization of O2 p and Zn 3d and stronger bonding–antibonding interaction between Zn 4 s (Ga 4 s, Li 2 s) and O 2p. Zn(1-x)(LiGa)(0.5x)O alloys have potential for applications such as ultraviolet (UV) light emitting devices and highly sensitive UV detectors to replace Zn1-xMgxO and Zn1-xBexO alloys due to the stable lattice structures and low band gap bowing.