Threading dislocations in thick layers of InxGa1-xN (5% < x < 15%) have been investigated by means of cathodoluminescence, time-resolved cathodoluminescence and molecular dynamics. We show that indium atoms segregate near dislocations in all the samples. This promotes the formation of In-N-In chains and atomic condensates which localize carriers and hinder non-radiative recombination at dislocations. We note however that the dark halo surrounding the dislocations in the cathodoluminescence

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... becomes increasingly pronounced as the indium fraction of the sample increases. Using transmission electron microscopy, we attribute the dark halo to a region of lower indium content formed below the facet of the V-shaped pit that terminates the dislocation in low composition samples (x < 12%). For x > 12%, the facets of the V-defect featured dislocation bundles instead of the low indium fraction region. In this sample the origin of the dark halo may relate to a compound effect of the dislocation bundles, of a variation of surface potential and perhaps of an increase in carrier diffusion length.