Effect of relaxation of the second-nearest neighbors on the thermodynamic properties of semiconducting alloys: Application to GaAsySb1−y

Abstract

We have studied the effect of relaxation of the second-nearest neighbors (NNN’s) in ${\mathrm{GaAs}}_{\mathrm{y}}$ ${\mathrm{Sb}}_{1\mathrm{-}\mathrm{y}}$ alloys by introducing a simple model which takes into account the difference in volume among the various configurations of the basic cluster. Using state-of-the-art density-functional theory, the ground-state properties of five different ordered structures have been calculated. It has been found that none of them is thermodynamically stable. Fixing the NNN overestimates by about 50% the strain energy and gives a miscibility gap of the disordered alloy larger than experiment, while upon relaxing the NNN excellent agreement with experiment is obtained.