Electron paramagnetic resonance of the group-III deep acceptor impurities in SiC

In this letter we report the EPR observation of the group-III deep acceptor impurities: deep B, deep Al and deep Ga centres in SiC crystals. A direct identification of the B and Ga atoms involved in the defect centre, considered as deep B and deep Ga, has been established by the presence of hyperfine interaction with B-11 and B-10 nuclei in isotope enriched B doped crystals and Ga-69 and Ga-71 nuclei in Ga doped crystals. In contrast to the results for the group-III shallow acceptor impurities in SiC, the observed qualitative behaviour for Al and Ga deep level impurities is the same as that for B. No effective-mass-like behaviour was observed for deep group-III accepters. Deep centres were shown from EPR spectra to have symmetry nearly axial around the hexagonal axis of the crystal. Evidence of strong thermally activated dynamic effects having common features for the EPR spectra of all deep centres have been observed. The structural model for deep centre as an impurity-vacancy pair are presented. For shallow B acceptor off-centre position of B which is induced by chemical rebonding was suggested and as a result no effective-mass-like behaviour was observed. It was indicated from ODMR of deep Al accepters that deep Al level is about 0.1 eV shallower as compared to deep B. Copyright (C) 1996 Published by Elsevier Science Ltd