The ground state, electronic and optical properties of the quaternary alloys BexCd1-xTeyS1-y /CdS for modeling quantum well lasers: Ab-initio study within modified Becke-Johnson exchange potential

Abstract

The ground state, electronic and optical properties of the quaternary BexCd1-xTeyS1-y lattice matched to CdS substrate has been predicated in detail via first principles calculations. A full potential linearized augmented plane wave (FP LAPW) method has been employed in conjunction with the generalized gradient approximation (GGA) to investigate the influence of increasing the concentration of beryllium and tellurium atoms with 0.25 step value (0 < x < 1 and 0 < y < 1) on the structural parameters such as the equilibrium lattice constant, the bulk modulus and its first pressure derivative. They were found in good agreement with the available data. Then, we have reported the concentration dependence on the improved electronic band structure and the optical constants (real and imaginary parts of the dielectric function and the refractive index) using the Modified Becke-Johnson exchange potential.For all Be and Te incorporated amounts with (x = y = 0.25, x = y = 0.5 and x = 0.5,y = 0.75), the BexCd1-xTeyS1-y lattice matched to CdS substrate alloys exhibits a semiconducting behavior with a small lattice mismatching ratio, a direct narrow band gaps energies and a high refractive index. Looking forward at the predominant field of expertise of these alloys, they can be futurely exploited in the designing of quantum well lasers based on BexCd1-xTeyS1-y active layer /CdS barrier.