ENDOR investigation of the microscopic structure of the boron acceptor in 6H-SiC

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Abstract
The boron acceptor in 6H-SiC was investigated using electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR). The hyperfine interactions with 11B could be determined precisely for the two quasi-cubic and the hexagonal sites. The microscopic model suggested from the EPR and ENDOR results is as follows: boron occupies a silicon site and is a negatively charged ligand to an adjacent carbon atom on which most of the unpaired spin density is located. At low temperatures the symmetry of the two quasi-cubic site defects is monoclinic, while the hexagonal site defect has C3V symmetry about the hexagonal axis. At about 50 K the two quasi-cubic site defects experience a thermally activated motion of the hole at the adjacent carbon about the hexagonal crystal axis and the apparent defect symmetry also becomes C3V. The boron acceptor should be regarded as a boron-induced carbon acceptor.