A new type of defects in Mg doped p-GaN films was detected and studied by means of microcathodoluminescence (MCL) imaging and electron beam induced current (EBIC) imaging in scanning electron microscope. The defects consist of small (about 10 mum) regions in which the MCL intensity is increased and the EBIC signal is decreased. Such behavior is explained by local increase of the hole density due to decreased concentration of compensating native donor defects. The density of these regions of enhanced hole concentration becomes higher and the characteristic dimensions lower in the samples with lower crystalline perfection which suggests diffusion controlled nucleation around nucleation sites. The defects of the above described nature are only detected in heavily Mg doped samples with the Mg concentration exceeding some 10(19) cm(-3) which is most likely related to less efficient formation of compensating donor defects in less heavily doped samples. (C) 2002 Elsevier Science Ltd. All rights reserved.