The results of density-functional plane-wave pseudopotential calculations for C and Si self-interstitials in cubic silicon carbide (3C-SiC) were reported. Several initial ionic configurations were used in the search for the global total-energy minimum; including tetragonal, split [100] and split [110] geometries. Neutral C interstitials were found to had several nearly degenerate total-energy minima configurations in split-interstitial geometries, with formation energies ranging—besides higher metastable ones—from 6.3 to 6.7eV in stoichiometric SiC. By contrast, the neutral Si interstitials had a clear single minimum total-energy configuration at the tetrahedral configuration with C nearest neighbors, exhibiting a formation energy of 6.0eV. The split interstitial in the [110] direction at the Si site and the tetrahedral configuration with Si nearest neighbors were metastable and had significantly higher formation energies. The present calculations indicated that the C interstitial introduces deep levels in the band gap while the Si interstitial at the tetrahedral site behaves like a shallow donor.

Self-Interstitials in 3C-SiC. J.M.Lento, L.Torpo, T.E.M.Staab, R.M.Nieminen: Journal of Physics - Condensed Matter, 2004, 16[7], 1053-60