A radiation-produced defect in GaN displaying hyperfine structure with three Ga atoms

Electron-irradiation of undoped n-type GaN with 2.5 MeV electrons at room temperature produces a broad PL band at similar to 0.95 eV, and an S = 1/2 ODEPR center, labeled L1, is observed in it. The L1 signal reveals partially resolved structure, which can be matched accurately as arising from hyperfine interaction with three equivalent Ga atoms. Irradiation in situ at 4.2 K produces the 0.95 eV band but the L1 ODEPR signal emerges only upon subsequent annealing at room temperature, as another ODEPR signal identified as interstitial Ga disappears. The possibility that both L1 and the 0.95 eV PL arise from the Ga vacancy is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.