Calculations of the structural and optoelectronic properties of cubic Cd_xZn_1−xSe_yTe_1−y semiconductor quaternary alloys using the DFT-based FP-LAPW approach

The structural and optoelectronic properties of technologically important Cd_xZn_1−xSe_yTe_1−y quaternary alloys have been calculated using the density functional theory (DFT)-based full potential (FP)-linearized augmented plane wave (LAPW) approach. The exchange–correlation potentials are calculated using the Perdew–Burke–Ernzerhof (PBE)-generalized gradient approximation (GGA) scheme for the structural properties and both the modified Becke–Johnson (mBJ) and Engel–Vosko (EV)-GGA schemes for the optoelectronic properties. A direct bandgap (\( \varGamma \)–\( \varGamma \)) is observed for all the examined compositions in the Cd_xZn_1−xSe_yTe_1−y quaternary system. At each cationic (Cd) concentration x, the lattice constant decreases while the bulk modulus and bandgap increase nonlinearly with increasing anionic (Se) concentration y. On the other hand, a nonlinear increase in the lattice constant but a decrease in the bulk modulus and bandgap are observed with increasing cationic concentration x at each anionic concentration y. The contour maps calculated for the lattice constant and energy bandgap will be useful for designing new quaternary alloys with desired optoelectronic properties. Several interesting features are observed based on the study of the optical properties of the alloys. The compositional dependence of each calculated zero-frequency limit shows the opposite trend, while each calculated critical point shows a similar trend, with respect to that found for the compositional dependence of the bandgap. Finally, the results of these calculations suggest that ZnTe, InAs, GaSb, and InP are suitable substrates for the growth of several zincblende Cd_xZn_1−xSe_yTe_1−y quaternary alloys.