Structural, electronic and optical properties of the wide band gap semiconductors KGaQ2 (Q = S, Se) and of AGaTe2 (A = K, Cs)

Abstract

In this paper, we studied the structural, electronic and some optical properties of KGaQ2 (Q = S, Se) and AGaTe2 (A = K, Cs) crystals using the pseudopotential plane-wave (PP-PW) method based on density functional theory (DFT), the generalized gradient approximation (GGA) parameterized by Perdew-Burke-Ernzerhof (GGA-PBE) is used for the exchange – correlation (XC) potential. We also use the hybrid density functional (HSE06) to study the electronic structures of these materials. Our results for the equilibrium lattice constants (a, b and c), angle β are in good agreement with experiment data. The electronic structure calculation suggested that crystals are direct-gap semiconductors, employing both the Perdew–Burke–Ernzerhof (PBE) and the hybrid (HSE06) functionals. We note that the hybrid density functional improved the value of band gap, and that the studied compounds are semiconductors with wide band gaps.  We have also predicted the optical properties; the refractive index, the reflection coefficient and dielectric constant on high frequencies.