Irradiation with 2.5MeV electrons in situ at 4.2K produced a broad photoluminescence band centered at 0.95eV. Optical detection of electron paramagnetic resonance in the band reveals two very similar, but distinct, signals, L5 and L6, which were identified as being interstitial Ga2+ in 2 different lattice configurations. L5, present immediately after the irradiation, was seen via a spin-dependent electron transfer process from the shallow effective-mass donor which competes with the photoluminescence (negative signal). L6 emerges upon annealing at various stages starting at ~60K, possibly assisted by optical excitation, as a spin-feeding process (positive signal) not involving the effective-mass donor. Both L5 and L6 disappear upon prolonged annealing at room temperature, with L6 disappearing first. Most of the 0.95eV band (~85%) also disappeared in this anneal, the remaining fraction being stable to ~500C. Two tentative models were presented, each of which identifies L5 and L6 with Ga2+ in different interstitial sites near the Ga vacancy from which they were created. Both models ascribe the 0.95eV photoluminescence band, along with an optical detection of electron paramagnetic resonance signal observed in it L1 as arising from the Ga vacancy, which in its isolated form was therefore stable to ~500C.

Intrinsic Defects in GaN - I. Ga Sub-Lattice Defects Observed by Optical Detection of Electron Paramagnetic Resonance. K.H.Chow, L.S.Vlasenko, P.Johannesen, C.Bozdog, G.D.Watkins, A.Usui, H.Sunakawa, C.Sasaoka, M.Mizuta: Physical Review B, 2004, 69[4], 045207 (9pp)