Optical manifestations of structural defects in unintentionally doped material were studied. A series of sharp peaks (labeled Yi with I = 1, 2, ..., 11) was observed in the low-temperature photoluminescence spectrum in the photon energy range between 2.6 and 3.46eV. The majority of these peaks was attributed 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.

Photoluminescence from Structural Defects in GaN. M.A.Reshchikov, J.Jasinski, Z.Liliental-Weber, D.Huang, L.He, P.Visconti, H.Morkoç: Physica B, 2003, 340-342, 440-3