Density-functional theory investigation of energy gaps and optical properties of Hg_1-xCd_xTe and In_1-xGa_xAs

We use a modified Becke-Johnson exchange plus a local density approximation correlation potential within the density functional theory to investigate the electronic structures of Hg_1-xCd_xTe and In_1-xGa_xAs with x being 0, 0.25, 0.5, 0.75, and 1. For both of the two series, our calculated energy gaps and dielectric functions (real part ε₁ and imaginary part ε₂) are in agreement with the corresponding experimental results with x being between 0 and 1. The calculated zero-frequency refractive index varies greatly with x for Hg_1-xCd_xTe, but changes little with x for In_1-xGa_xAs, which is consistent with the real parts of their dielectric functions. Therefore, this new approach is satisfactory to describe the electronic structures and the optical properties of the semiconductors.