Electronic and Optical Properties of Spinel GeMg₂O₄ and GeCd₂O₄

Oxide spinels have potential applications in optoelectronics and optics fields. In this work the electronic band structure and optical properties of GeMg₂O₄ and GeCd₂O₄ are calculated by first principles technique based on the new potential approximation known as the modified Becke–Johnson exchange potential approximation (mBJ). The local density and generalized gradient approximations significantly underestimate the direct band gap values compared to the mBJ. The band gap dependent optical parameters such as dielectric constant, refractive index, reflectivity and optical conductivity are calculated and analyzed. The replacement of the cation is observed and analyzed for the compounds studied and a prominent change is noticed. The replacement of the cation Mg by Cd reduces the band gap and its dependent optical parameters. For device fabrication in different regions of the spectrum this variation is strongly recommended.