First-principles calculations on the origins of the gap bowing in InAs1-xPx alloys

We perform self-consistent ab-initio calculations to study the structural, electronic and thermodynamic properties of InAs_1-xP_x alloy. The full potential-linearized augmented plane wave (FP-LAPW) method was employed within density functional theory (DFT). The ground-state properties are determined for the bulk materials (InAs and InP) as well as for the different concentration of their alloys. Deviations of the lattice constants from Vegard's law and the bulk modulus from linear concentration dependence (LCD) were observed. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. The gap bowing for the alloy of interest was found to be mainly caused by the charge-exchange contributions. In addition, the thermodynamic stability of InAs_1-xP_x alloy was investigated by calculating the excess enthalpy of mixing ΔH_m and the calculated phase diagram showed a broad miscibility gap with a high critical temperature.