Irradiation of undoped n-type GaN with 2.5MeV electrons at room temperature produced a broad photoluminescence band at about 0.95eV, and an S=1/2 optically-detected electron paramagnetic resonance center, labelled L1, was observed. The L1 signal revealed a partially resolved structure which was attributed to hyperfine interactions with 3 equivalent Ga atoms. Irradiation in situ at 4.2K produced the 0.95eV band, but the L1 optically-detected electron paramagnetic resonance signal emerged only during subsequent annealing at room temperature as another optically-detected electron paramagnetic resonance signal, attributed to interstitial Ga, disappeared. The possibility was considered that both L1 and the 0.95eV photoluminescence arose from the Ga vacancy.

A Radiation-Produced Defect in GaN Displaying Hyperfine Structure with Three Ga Atoms. G.D.Watkins, L.S.Vlasenko, C.Bozdog: Physica B, 2001, 308-310, 62-5