First-principle calculations of dilute nitride GaP1−xNx alloy in zinc-blende structures

First-principle plane-wave pseudopotential calculations using the density-functional theory within the local density approximation (LDA) have been carried out to investigate the structural, electronic and thermodynamic properties of zinc-blende dilute nitride GaP_1−xN_x alloy. We have found that the unit cell volumes of GaP_1−xN_x alloys are smaller than the value calculated from the linear interpolation of GaN and GaP binary alloys and there exists a negative deviation from Vegard's law. The Ga-P and Ga-N bond lengths of GaP_1−xN_x alloys reveal a slight relaxation. The incorporation of nitrogen into GaP leads to the giant reduction of the bandgap energy. We have investigated the thermal stabilities and obtained the most stable configurations of the GaP_1−xN_x alloy. In addition, the formation enthalpies have also been calculated, which could explain the difficulty in nitrogen incorporation into GaP.