Optical and structural properties of dislocations in InGaN

Massabuau, F.C-P. and Horton, M.K. and Pearce, E. and Hammersley, S. and Chen, P. and Zielinski, M.S. and Weatherley, T. and Divitini, G. and Edwards, P.R. and Kappers, M.J. and McAleese, C. and Moram, M.A. and Humphreys, C.J. and Dawson, P. and Oliver, R.A. (2019) Optical and structural properties of dislocations in InGaN. Journal of Applied Physics, 125 (16). 165701. ISSN 0021-8979

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    Abstract

    Threading dislocations in thick layers of In x Ga 1-x N (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 nonradiative recombination at dislocations. We note, however, that the dark halo surrounding the dislocations in the cathodoluminescence image 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.