Magneto-optical studies of the 0.88-eV photoluminescence emission in electron-irradiated GaN

Properties of the 0.88-eV photoluminescence (PL) in electron-irradiated wurtzite GaN have been investigated in detail by a combination of various magneto-optical techniques, including Zeeman measurements of PL, optically detected magnetic resonance (ODMR), and level anticrossing (LAC). ODMR observed by monitoring the PL emission is demonstrated to originate from a spin triplet. The symmetry of the corresponding defect is shown to be rhombic with its principal axes pointing into the high-symmetry directions Z=[0001], Y=[11¯00], and X=[112¯0]. From the Zeeman measurements the emission is shown to arise from an optical transition between a singlet excited state and the singlet ground state, providing convincing evidence for indirect detection of the spin triplet ODMR. LAC investigations of the same PL emission reveal two LAC lines, among which one is related to the spin triplet detected in ODMR.