Electronic and Optic Properties of Cubic Spinel CdX2O4 (X=In, Ga, Al) through Modified Becke?Johnson Potential

A new potential approximation known as modified Becke?Johnson based on density functional theory is applied to compute the electronic band profile and optical response of CdIn2O4, CdGa2O4 and CdAl2O4 compounds. The direct band gap with common LDA, GGA and EV-GGA is drastically underestimated compared with modified Becke?Johnson approximation, whose results are significantly closer to the experimental findings. The optical properties like dielectric constant, refractive index, reflectivity, optical conductivity and absorption coefficient are also computed. A unique characteristic associated with cation replacement is studied; the replacement of cation In by Ga and Ga by Al significantly reduces the direct energy band gap in these compounds. This variation is of crucial importance for band gap dependent optical properties of these compounds, which is also proof for applications of these compounds in optoelectronic devices.