Photoluminescence spectroscopy was used to determine the nature of a near-infrared photoluminescence emission, with a no-phonon line at about 0.88eV, which was often present in electron-irradiated material. This emission was suggested to originate from an internal transition between a moderately shallow excited state of a deep defect, with an ionization energy of about 0.021eV, and a deep ground state, with an ionization energy of about 0.9eV. The existence of a higher-lying second excited state, which was related to the 0.88eV photoluminescence center, was also revealed by temperature-dependent studies. A different electronic character of the wave functions, which was related to the first and second excited states, was revealed by photoluminescence polarization measurements. Since the photoluminescence emission was observed to have a comparable intensity for all electron-irradiated samples, regardless of doping, it was proposed that either native defects or common residual contaminants (or their complexes) were involved. The substitutional ON donor (or related complex) was considered to be the most probable candidate. This conclusion was based on a marked similarity between the local vibrational properties of the 0.88eV photoluminescence centers and the substitutional OP donor in GaP.

Electronic Structure of the 0.88eV Luminescence Center in Electron-Irradiated Gallium Nitride. I.A.Buyanova, M.Wagner, W.M.Chen, N.V.Edwards, B.Monemar, J.L.Lindström, M.D.Bremser, R.F.Davis, H.Amano, I.Akasaki: Physical Review B, 1999, 60[3], 1746-51