An investigation was made of radiation-induced defects, in neutron-irradiated and subsequently annealed 6H-SiC, using electron paramagnetic resonance, magnetic circular dichroism of absorption and MCDA-detected electron paramagnetic resonance. In samples which were annealed beyond the annealing temperature of the isolated Si vacancy, photo-induced electron paramagnetic resonance spectra of spin S = 1 centers that occurred in the orientations expected for nearest-neighbor pair defects were observed. The electron paramagnetic resonance spectra of the defect on the 3 inequivalent lattice sites were resolved and attributed to optical transitions between photon energies of 0.999 and 1.075eV by MCDA-detected electron paramagnetic resonance. The resolved hyperfine structure indicated the presence of a single C nucleus and of several Si ligand nuclei. The data were interpreted with the aid of total-energy and spin density data obtained from the standard local-spin density approximation of density-functional theory; using relaxed defect geometries which were obtained from the self-consistent charge density-functional theory-based tight-binding scheme. Several defect models were checked, of which only the photo-excited spin triplet state of the C antisite–C vacancy pair (CSi-VC) in the doubly-positive charge state could explain all of the experimental findings. It was proposed that the (CSi-VC) defect was formed from the isolated Si vacancy, as an annealing product, by the movement of a C neighbor into the vacancy.

Structure of the Silicon Vacancy in 6H-SiC after Annealing Identified as the Carbon Vacancy–Carbon Antisite Pair. T.Lingner, S.Greulich-Weber, J.M.Spaeth, U.Gerstmann, E.Rauls, Z.Hajnal, T.Frauenheim, H.Overhof: Physical Review B, 2001, 64[24], 245212 (10pp)