Formation and vanishing of short range ordering in GaAs_1-xBi_x thin films, G. Ciatto, M. Thomasset, F. Glas, X. F. Lu, T. Tiedje, Phys. Rev. B 82, 201304 (2010)

We address the compositional evolution of the structure of GaAs_1-xBi_x thin films at different scale lengths by combining x-ray absorption spectroscopy, atomic force microscopy, and x-ray diffraction. We find that Bi short range ordering, observed for x <3%, drastically vanishes for x >5.4%. The recovery of random anion distribution goes along with the formation of Bi droplets at the sample surface while bulk maintains high crystalline quality. These structural changes go with the anomalous behavior of optical and electronic properties. In particular, we find that the decrease in emission intensity in the samples corresponds to the concentration point where Bi short range ordering is lost, hence the preservation of nonrandom distribution turns to be a key point in devices design.