Electron paramagnetic resonance of defects with metastable properties in crystalline GaN

An EPR study of GaN revealed the presence of defects exhibiting metastable properties. EPR spectra of two centers (ii1a and ii1b) with axial symmetry along the hexagonal axis of the crystal, which have strongly anisotropic g factors, were observed. The anisotropy of the spectra decreases, and the line shape changes, with increasing temperature. The spectra of the ii1a and ii1b centers disappear at 25 and 50 K, respectively. Subsequent cooling of the samples does not restore the EPR signals, which implies that one observes here phenomena inherent in defects with metastable states. To restore EPR signals, one has to warm the samples to room temperature under very specific conditions. The possible microstructure of the discovered defects is discussed. Fiz. Tverd. Tela (St. Petersburg) 40, 1818–1823 (October 1998)