We have examined the alloy composition dependence of the energy bandgap and electronic states in GaAsNBi alloys. Using direct measurements of N and Bi mole fractions, via ion beam analysis, in conjunction with direct measurements of the out-of-plane misfit via x-ray rocking curves, we determine the “magic ratio” for lattice-matching of GaAsNBi alloys with GaAs substrates. In addition, using a combination of photoreflectance and photoluminescence spectroscopy, we map the composition- and misfit-dependence of the energy bandgaps, along with revealing the energetic position of Bi-related states at approximately 0.18 eV above the valence band maximum.

Photoreflectance measurements were performed for GaAs1−x−yNxBiy layers in the temperature range of 20–300 K. For each sample a transition related to the band-gap was observed, which red-shifts with increasing nitrogen and bismuth content. The temperature dependencies of the band-gap were fitted by the Varshni and Bose–Einstein formulas and simulated within the band anticrossing model of the interaction between the extended band states of the GaAs and the localized states associated with nitrogen and bismuth atoms. The reduction of the band-gap was found to be ∼80–100 meV.