Radiation-induced defects in GaN

Radiation-induced defects in n-type GaN irradiated by 2 MeV electrons at room temperature were studied by electron paramagnetic resonance (EPR). Four EPR spectra, labelled D1–D4, were observed in irradiated n-type GaN. The D1 spectrum is a broad line (∼10–12 mT in line width) with an isotropic g -value g ∼2.03 and can be detected in all the studied samples in the temperature range of 4–300 K. The D2 centre has an electron spin S =1/2 and shows a clear hyperfine structure due to interaction with three equivalent 14 N. The g -values of the axial configuration are determined to be g ∥ =2.001 and g ⊥ =1.999. On the basis of the observed hyperfine structure, formation conditions and annealing behaviour, the D2 defect was assigned to the gallium vacancy–oxygen pair in the negative charge state, (V Ga O N ) – .