Cathodoluminescence intensity and dislocation contrast evolutions under electron beam excitation in epitaxial GaN laterally overgrown on (0001) sapphire

We describe the first stage of the evolution of CL spectra, intensity and dislocation contrast under low keV electron beam for ELO-GaN with a low dislocation density. The UV and yellow intensities are decreased by beam irradiation. We have observed a broadening of the UV peak towards low energies followed by a red shift. This is explained in terms of an electron beam activation of non-radiative centers which relax partially the compressive strain, The dislocation contrast is lowered, but the dislocations become more non-radiative. We suggest that dislocations are preferential ways for the flux of non-radiative centers from the coalescence boundaries to the bulk. (C) 1999 Elsevier Science B.V. All rights reserved.