How much room for BiGa heteroantisites in GaAs1-xBix?

We addressed the issue of bismuth heteroantisite defects (BiGa) in GaAs1-xBix/GaAs epilayers by coupling x-ray absorption spectroscopy at the bismuth edge with density functional theory calculations of the defect structure. Calculations predict a large relaxation of the Bi-As interatomic distances when Bi atoms substitute Ga, however we found no experimental evidence of it. Quantitative analysis of the x-ray absorption spectra allows us to establish a maximum concentration limit for Bi_Ga, which corresponds to about 5% of the total Bi atoms. Bi_Ga do not account for the modifications in the spectra previously attributed to short range ordering.