Structural and electronic properties of the wide-gap Zn_1−<i>x</i>Mg_<i>x</i>S, Zn_1−<i>x</i>Mg_<i>x</i>Se and Zn_1−<i>x</i>Mg_<i>x</i>Te ternary alloys

Abstract

Zn1−x Mg x S, Zn1−x Mg x Se and Zn1−x Mg x Te ternary wide-gap semiconductor alloys were investigated using the full potential–linearized augmented plane wave (FP-LAPW) method. We have studied the effect of composition on structural properties such as lattice constants, bulk modulus and bond ionicity. The bandgap and the microscopic origins of compositional disorder have also been explained in detail. In addition, from the obtained band structures, the electron (hole) conduction and valence effective masses are deduced. These parameters were found to depend non-linearly on alloy composition x ,e xcept the lattice parameter for Zn1−x Mg x S, which follows Vegard’s law. The calculated band structures for all three alloys show a direct bandgap in the whole range of x composition. We have paid special attention to the disorder parameter (gap bowing). Using the approach of Zunger and co-workers, we have concluded that the total bandgap energy bowing was mainly caused by the charge exchange effect for the alloys of interest.