First-principles prediction of the structural and electronic properties of zinc blende GaNxAs1−x alloys

To investigate the structural and electronic properties of zinc blende GaNxAs1−x alloys, we performed full-potential linearized augmented plane wave (FP-LAPW) calculations based on density functional theory. We assessed GaNxAs1−x alloys for 0≤x≤1 using 16-atom special quasi-random structures. The generalized gradient approximation (GGA) of Wu and Cohen was used as the exchange correlation potential to calculate the structural and electronic properties of GaNxAs1−x. In addition, the alternative GGA proposed by Engel and Vosko and the modified Becke–Johnson potential were used for better reproduction of the band structure and electronic properties. The equilibrium lattice parameters and bulk modulus were calculated and analyzed for binary and ternary alloys. The lattice constants for GaNxAs1−x positively deviate from Vegard's law with an upward bowing parameter of −0.4708 Å. All our materials are direct-bandgap semiconductors for which the valence band maximum is located at Γv and the conduction band minimum at Γc. We observed that the direct bandgap of GaNxAs1−x increases nonlinearly with x. To shed light on the bandgap trend for increasing nitrogen concentrations in GaNxAs1−x, we used the atoms-in-molecule formalism. Special attention was paid to the increase in charge transfer for the nitrogen atom and to ionicity as a function of increasing x concentration.