The annealing product of the silicon vacancy in 6H–SiC

Abstract

Radiation-induced defects in 6H-silicon carbide were investigated with electron paramagnetic resonance (EPR), the magnetic circular dichroism of the absorption (MCDA) and MCDA-detected EPR (MCDA-EPR). In irradiated samples, annealed beyond the annealing temperature of the isolated silicon vacancy (V Si), we observed photo-EPR spectra of spin S=1 centers, having the symmetry of nearest neighbor pair defects. By MCDA-EPR, they were associated to optical transitions with photon energies between 999 and 1075 meV. The hyperfine structure of the EPR spectra shows the presence of one single carbon and several silicon ligands. The experimental results are interpreted with the help of total energy and spin density data obtained from the standard local-density approximation of the density-functional theory, using relaxed defect geometries obtained from the self-consistent charge density-functional theory based tight binding scheme. The only model that explains all experimental findings is the photo-excited spin triplet state of the carbon antisite–carbon vacancy pair (C Si–V C) in the doubly positive charge state. We conclude that the C Si–V C defect is formed from V Si as an annealing product by the movement of a carbon neighbor into the vacancy.