Continuous redshift of an emission from 3.23 to 2.85 eV with decreasing excitation density is observed in the photoluminescence spectra of highly doped GaN:Mg. It has been explained by the formation of minibands originating from the overlap of deep levels and shallow acceptor levels. For nominally undoped samples the intensity ratio of a donor-bound exciton line and a donor–acceptor pair line changes dramatically with excitation density due to the limited number of acceptors. ©1998 American Institute of Physics.