Electronic structure of carbon antisite in SiC: localization versus delocalization

In paper (Baranov et al., 2008 [26]) the EPR spectrum with large 13C isotope hyperfine splitting was observed in neutron-irradiated 6H-SiC crystals and attributed to the positively charged carbon antisite CSi+. However up till now numerous ab initio calculations show that this defect is optically and electrically inactive and hence it cannot be detected in experiment. In the present paper we have considered carbon antisite in framework of DFT with self interaction correction. We show that small polaron-like ground state with broken bond configuration may be formed in the case of positively charged carbon antisite CSi+ while for negatively charged defect formation of such state is energy-unprofitable. For unambiguous identification of carbon antisite the parameters of hyperfine interaction with central carbon CSi as well as with four nearest carbons were calculated and compared with EPR experiment both for positively and negatively charged centers.