Self-assembling of zinc and tellurium impurities in zinc-blende MgS

Conditions providing a thermodynamic advantage governing the self-assembly of Zn and Te impurities in metastable magnesium sulfide (MgS) with zinc-blende structure have been theoretically studied. The formation of tetrahedral 1Te4Zn cells is thermodynamically favorable in Zn_xMg_{1 ? x} Te_yS_{1 ? y} (x ≥ 4y) solid solutions enriched in MgS in the region of dilute Te concentrations. At temperatures selected for the growth (230°C) and annealing (500°C), the free energy of a solid solution in which separate Te atoms must be surrounded only by Zn atoms is lower than that of the solution with a random arrangement of these impurities. This phenomenon is due to a thermodynamic advantage of the formation of Mg-S and Zn-Te bonds over Zn-S and Mg-Te bonding, as well as due to a decrease in the elastic strain energy upon self-assembly of the given isoelectronic impurities.