Transmission electron microscopy studies of the core structure and opto-electronic properties of dislocations in GaN films were described. It was shown that the core structure depends sensitively on the growth method and on the presence of dopants and impurities including Si, Mg and O, with edge, screw and mixed dislocations all becoming open core type under certain conditions. High-resolution electron energy-loss spectroscopy was used to confirm impurity segregation to dislocations. Electron holography and cathodoluminescence studies showing that dislocations possess band gap states and act as non-radiative recombination centers were reviewed, and correlated, tentatively, to impurity segregation.

The Structure and Properties of Dislocations in GaN. D.Cherns, M.E.Hawkridge: Journal of Materials Science, 2006, 41[9], 2685-90