Photoluminescence from structural defects in GaN

We studied optical manifestation of structural defects in unintentionally doped GaN. A series of sharp peaks (labeled as Yi with i=1,2,y,11) was observed in the low-temperature photoluminescence spectrum in the photon energy range between 2.6 and 3.46 eV. We attribute the majority of these peaks to excitons bound to yet unidentified structural defects. A preliminary transmission electron microscopy study in one of the samples exhibiting strong Yi lines revealed numerous inclusions, presumably inversion domains, which may be responsible for at least some of the Yi lines.