Identification of Burgers vectors along <111> in In-doped GaAs, by X-ray transmission topography and image simulation

Long dislocations with Burgers vectors along <111> are unusual in f.c.c. lattices. X-ray topographs have been obtained of as-grown GaAs crystals doped with 10²⁰ atoms cm^-3 of In, where the usual extinction criterion g.b = 0 leads to this type of defect. However, for several g satisfying the condition g.b = 0 with b = a [111], the images of these dislocations were still clearly visible. Comparison between experimental and computer-simulated X-ray topographic sections of these defects confirms the existence of Burgers vectors along <111>.