Using first-principles total energy calculations, a study was made of the structural properties of the large lattice mismatched GaAs1–xNx alloys. The validity of Vegard’s law was first considered, which latter assumed a linear variation of the alloy concentration with both lattice constant and volume. In the dilute-N limit, the calculated lattice constant coincided with Vegard's law for the lattice constant, but not for the volume variation. This deviation implied that using Vegard's law for the volume variation overestimated the N concentration. In the dilute-As limit, the calculated lattice constant was larger than that suggested by the Vegard's law for both the volume and the lattice constant, implying that using Vegard's law overestimated the As concentration. The calculated bulk moduli for GaAs1–xNx, however, showed almost linear behavior in the two region, increased monotonically with N concentration. The effect of the split interstitial defect, (N-N)spl, upon the electronic and structural properties of the alloy was also studied. It was found that the split interstitial was an amphoteric defect with (+/0) transition at 0.2eV and (0/–) transition at 0.3eV above the valence band maximum. The concentration of the split N interstitial [N-N] was relatively small compared to the substitutional N, but it would be large if the system could be grown at the As-rich limit and the sample were doped n-type.

Evolution of Structural Properties and Formation of N-N Split Interstitials in GaAs1–xNx Alloys. P.Carrier, S.H.Wei, S.B.Zhang, S.Kurtz: Physical Review B, 2005, 71[16], 165212 (5pp)