The isolated negatively charged Si vacancy (VSi-) in the hexagonal lattices of 4H- and 6H-SiC was studied by electron paramagnetic resonance. The local structure was suggested to have Td symmetry from the isotropic g-value within the resolution of the conventional X-band measurements, from the isotropic 29Si hyperfine interaction of the next-nearest-neighbor Si atoms and from the absence of the zero-field splitting with the high spin state of S = 3/2. From the 13C hyperfine spectrum of the nearest-neighbor C atoms, the two kinds of VSi-, denoted VSi-(I) and VSi-(II), respectively were distinguished. The VSi-(I) and VSi-(II) were assigned to be arising from hexagonal site (h) and quasi-cubic sites (k in 4H-SiC, k1 and k2 in 6H-SiC), respectively. In both VSi-(I) and VSi-(II), from the 13C hyperfine interactions, the symmetry was revealed to be C3v with the arrangement of the four nearest-neighbor C atoms slightly distorted from a regular tetrahedron.

EPR Studies of the Isolated Negatively Charged Silicon Vacancies in n-Type 4H- and 6H-SiC - Identification of C3v Symmetry and Silicon Sites. N.Mizuochi, S.Yamasaki, H.Takizawa, N.Morishita, T.Ohshima, H.Itoh, J.Isoya: Physical Review B, 2003, 68[16], 165206 (11pp)