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 acc eptor 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 crys tals. In contrast to the results for the group-III shallow acceptor im purities in SiC, the observed qualitative behaviour for Al and Ga deep level impurities is the same as that for B. No effective-mass-like be haviour was observed for deep group-III accepters. Deep centres were s hown from EPR spectra to have symmetry nearly axial around the hexagon al axis of the crystal. Evidence of strong thermally activated dynamic effects having common features for the EPR spectra of all deep centre s have been observed. The structural model for deep centre as an impur ity-vacancy pair are presented. For shallow B acceptor off-centre posi tion of B which is induced by chemical rebonding was suggested and as a result no effective-mass-like behaviour was observed. It was indicat ed from ODMR of deep Al accepters that deep Al level is about 0.1 eV s hallower as compared to deep B. Copyright (C) 1996 Published by Elsevi er Science Ltd