First-principles investigation of wide-gap quaternary alloys Zn1−xMgxSyTe1−y

We investigate the structural and electronic properties of (Zn, Mg) (S, Te) solid solutions using the full potential-linearized augmented plane wave method within density functional theory. We use the generalized gradient approximation that is based on exchange–correlation energy optimization for calculating the total energy. Moreover, the Engel–Vosko GGA formalism is applied so as to optimize the corresponding potential for band gap calculations. We study the effect of composition on lattice constant, bulk modulus and band gap for pseudobinary as well as for quaternary alloys which showed nonlinear dependence on the composition. The bowing of the fundamental gap versus composition predicted by our calculations is in very good agreement with experiments available for pseudobinary alloys. In addition, the energy band gap of zinc-blende Zn1−xMgxSyTe1−y quaternary alloys lattice matched to GaAs substrate is investigated. It should be noted that the present work is the first theoretical study of the quaternary alloys of interest.