Theoretical study on electronic and optical properties of Zn-doped In0.25Ga0.75As photocathodes

First-principles calculations for intrinsic and Zn-doped In0.25Ga0.75As are performed based on density functional theory to study the influence of Zn doping on electronic and optical properties. The band structure, density of state, Mulliken population, dielectric function, complex refractive index, absorption coefficient and reflectivity of In0.25Ga0.75As are calculated. Results show that the Fermi levels of two Zn-doped models enter into the valence bands and Zn atom is more easily to replace In atom than Ga atom. The lattice constant of In0.2344Ga0.75-Zn0.0156As reduced after optimization, while that of In0.25Ga0.7344Zn0.0156As increased to the contrary. The Mulliken bond population shows that the doping Zn atoms can enlarge the strength of In-As and Ga-As polar covalent bonds. Furthermore, the calculated absorption coefficient and reflectivity are used to characterize the performance of photoemission, indicates that the photoresponses of Zn-doped models are better than that of the intrinsic.