The effect of Ni/Co-doping on electronic structures and optical properties of cubic Ca2Ge

Abstract

The electronic structures and optical properties of the intrinsic, Ni-, Co-, and CoNi-doped models of cubic Ca2Ge alloys have been investigated by using the plane wave ultra-soft pseudopotential method based on the density functional theory. The doped metal ions cause lattice distortion (the lattice constant decreases slightly) and enhance the built-in electric field. As a result, in the low energy zone, the dielectric constant, the refractive index, and the extinction coefficient increase; with the appearance of impurity bands, the width of the band gap reduces significantly; and the absorption spectrum redshifts, indicating a stronger response in the infrared band, and a higher light utilization efficiency. In addition, the CoNi-doped results in the best enhancement in optical properties in the low energy region.