Transition from optically inactive to active Mg-chalcogenides: A first principle study

Density functional calculations of the structural, electronic and optical properties of MgSxSe1−x, MgSxTe1−x and MgSexTe1−x, in the composition range from x = 0 to x = 1, are carried out using the highly accurate mBJ potential with the full potential linearized augmented plane waves (FP-LAPW) method. The calculated lattice constants follow Vigard’s law while other properties like bulk moduli, band gaps and optical properties vary nonlinearly with the concentration (x). The binary magnesium chalcogenides, MgS, MgSe and MgTe, are wide and indirect band gap materials, whereas it is found that their ternaries are of direct band gap nature. Indirect band gaps materials are inactive material and could not be used as luminescent materials. The wide and direct band gaps of these alloys predict that they can be efficiently used in optoelectronic devices. Therefore, the optical properties of direct band gap ternary alloys are also calculated.

► MgS, MgSe and MgTe in rock salt phase are optically inactive.
► It is found that MgSSe, MgSTe and MgSeTe are optically active.
► Optical properties of MgSSe, MgSTe and MgSeTe are investigated.
► Bandgap bowing and structural properties of the compounds are also investigated.