Electronic structure and optical properties of bulk In0.53Ga0.47As for near-infrared photocathode

In0.53Ga0.47As is a new near-infrared material for negative electron affinity photocathodes. Geometry optimization combined generalized gradient approximation based on the density functional theory is adopted to calculate the bulk In0.53Ga0.47As. Lattice constant of bulk In0.53Ga0.47As after geometry optimization is compared with the theoretical one based on the Vigard law, which proves the reliability of the parameters of the geometry optimization. The energy bands, electronic structures and optical properties of the bulk ternary In0.53Ga0.47As for near-infrared photocathode are analyzed. Electron transition way which is closely related with the photoemission is analyzed from the energy bands and the density of electrons. The dielectric function and the optical absorption coefficient are made clear based on the partial density of states. It is found that optical absorption coefficient of bulk In0.53Ga0.47As is bigger than that of GaAs in the near-infrared band, which is in keeping with the experiments. The analysis provides a theoretical foundation to design a better near-infrared negative electron affinity photocathode from the point of microscopic atoms.