Radiation-induced defects in 6H-type material were investigated by using electron paramagnetic resonance, magnetic circular dichroism of absorption (MCDA) and MCDA-detected electron paramagnetic resonance. In irradiated samples, when annealed beyond the annealing temperature of the isolated Si vacancy (VSi), photo-electron paramagnetic resonance spectra of spin S = 1 centers which had the symmetry of nearest-neighbor pair defects were observed. The MCDA-electron paramagnetic resonance data showed that they were associated with optical transitions having photon energies of between 0.999 and 1.075eV. The hyperfine structure of the electron paramagnetic resonance spectra revealed the presence of a single C, and several Si ligands. The experimental results were interpreted with the help of total energy and spin density data obtained from the standard local-density approximation of density-functional theory; using relaxed defect geometries, obtained from a self-consistent charge density-functional theory based tight-binding scheme. The only model that explained all of the experimental results was the photo-excited spin triplet state of the C antisite–C vacancy pair (CSi–VC) in the doubly-positive charge state. It was concluded that the CSi–VC defect was formed from VSi, as an annealing product; via the movement of a C neighbor into the vacancy.

The Annealing Product of the Silicon Vacancy in 6H–SiC. T.Lingner, S.Greulich-Weber, J.M.Spaeth, U.Gerstmann, E.Rauls, H.Overhof: Physica B, 2001, 308-310, 625-8