Nature of the 2.8 eV photoluminescence band in Mg doped GaN

The blue Mg induced 2.8 eV photoluminescence (PL) band in metalorganic chemical vapor deposition grown GaN has been studied in a large number of samples with varying Mg content. It emerges near a Mg concentration of 1×1019 cm−3 and at higher concentrations dominates the room temperature PL spectrum. The excitation power dependence of the 2.8 eV band provides convincing evidence for its donor–acceptor (D–A) pair recombination character. It is suggested that the acceptor A is isolated MgGa while the spatially separated, deep donor (430 meV) D is attributed to a nearest-neighbor associate of a MgGa acceptor with a nitrogen vacancy, formed by self-compensation.