Ground state and phase stability of GaP-ZnS and GaP-ZnSe quaternary systems from first-principles

Abstract

Quaternary alloys systems with large direct bandgap are promising for electronic devices and energy applications. Here we performed a crystal structure search for GaP-ZnS and GaP-ZnSe quaternary alloys using an ab initio evolutionary algorithm. The analysis of structures reveals the existence of trigonal (R3m) phases for GaPZnS and GaPZnSe alloys, which are thermodynamically slightly unstable, but dynamically and mechanically stable. State-of-the-art local density approximation half-occupation (LDA-1/2) approach divulges that both materials exhibit wide band-gap character (EG(x)∼2.78eV, and 2.48eV for GaPZnS and GaPZnSe respectively). Moreover, GaPZnS is found to be indirect; whereas GaPZnSe evinces a quasi-direct band-gap character. Besides, we predict a relatively weak band-gap bowing of 0.84eV for GaPZnS and 0.96eV for GaPZnSe quaternary alloys.