Defect diffusion and strain relaxation in epitaxial GaN laterally overgrown on (0001) sapphire under low energy electron beam irradiation

In situ cathodoluminescence experiments have been performed to follow the t ime dependence of the UV luminescence in epitaxial lateral overgrowth GaN s pecimens. The decrease of the observed intensity and red-shift of the UV pe ak are interpreted in terms of non-radiative defect introduction and diffus ion. This leads to strain relaxation of the GaN epilayer, which is initiall y under compressive strain. Monochromatic UV and yellow CL images show that dislocations act as efficient non-radiative recombination centres, that th ey are not at the origin of the yellow band and that they do not move under the electron beam.