Abstract
We have studied the effect of depositing a Mg-doped GaN cap layer on near-ultraviolet emitting In0.05Ga0.95N/Al0.05Ga0.95N multiple quantum well structures, using photoluminescence spectroscopy and transmission electron microscopy. The room temperature (T = 300 K) photoluminescence spectra revealed a reduction in the integrated photoluminescence intensity of the capped structure, which is shown by time decay measurements to be due to greater competition from non-radiative recombination processes. The structural analysis of the samples using electron microscopy has not shown any evidence of Mg-induced defects. We suggest that the non-radiative recombination path is related to the diffusion of Mg atoms into the quantum well region and the formation of Mg-nitrogen vacancy complexes. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.