Electronic band structure of nitrogen diluted Ga(PAsN): Formation of the intermediate band, direct and indirect optical transitions, and localization of states

The electronic band structure of Ga(PAsN) with a few percent of nitrogen is calculated in the whole composition range of Ga(PAs) host using density functional methods including the modified Becke-Johnson functional to correctly reproduce the bandgap and unfolding of the supercell band structure to reveal the character of the bands. Relatively small amounts of nitrogen introduced to Ga(PAs) lead to the formation of an intermediate band below the conduction band, which is consistent with the band anticrossing model, widely used to describe the electronic band structure of dilute nitrides. However, in this study, calculations are performed in the whole Brillouin zone and they reveal the significance of the correct description of the band structure near the edges of the Brillouin zone, especially for the indirect bandgap P-rich host alloy, which may not be properly captured with simpler models. The influence of nitrogen on the band structure is discussed in terms of the application of Ga(PAsN) in optoelectronic devices such as intermediate band solar cells, light emitters, as well as two color emitters. Additionally, the effect of nitrogen incorporation on the carrier localization is studied and discussed. The theoretical results are compared with experimental studies, confirming their reliability.