ODMR studies of As-grown and electron-irradiated GaN and AIN

In a thin epilayer of wurtzite GaN grown on sapphire, electron irradiation strongly quenches the visible luminescence, producing a set of new overlapping bands in the infrared at similar to 0.85 and similar to 0.93 eV. Four new ODMR signals are detected in these bands, one of them, LE3, displaying resolved "hyperfine-like" structure. The origin of this structure is presently not understood, however. In as-grown small single crystals of AlN, many well resolved strongly anisotropic ODMR signals are detected. The main effect of electron irradiation is to enhance one of signals, an S = 1/2 signal near g similar to 2, whose flat-topped shape suggests possible unresolved hyperfine interaction with a single nucleus.