EPR studies of the isolated negatively charged silicon vacancies in n-type 4H- and 6H-SiC:: Identification of C3υ symmetry and silicon sites -: art. no. 165206

The isolated negatively charged silicon vacancy (V-Si(-)) in the hexagonal lattices of 4H- and 6H-SiC has been studied by electron paramagnetic resonance (EPR). The local structure was suggested to have T-d symmetry from the isotropic g value within the resolution of the conventional X-band measurements, from the isotropic Si-29 hyperfine interaction of the next-nearest-neighbor silicon atoms and from the absence of the zero-field splitting with the high spin state of S=3/2. From the C-13 hyperfine spectrum of the nearest-neighbor carbon atoms, the two kinds of V-Si(-), denoted V-Si(-)(I) and V-Si(-)(II), respectively have been distinguished. V-Si(-)(I) and V-Si(-)(II) are assigned to be arising from hexagonal site (h) and quasicubic sites (k in 4H-SiC, k(1) and k(2) in 6H-SiC), respectively. In both V-Si(-)(I) and V-Si(-)(II), from the C-13 hyperfine interactions, the symmetry has been revealed to be C-3v with the arrangement of the four nearest-neighbor carbon atoms slightly distorted from a regular tetrahedron.