The photoluminescence center DII was a persistent intrinsic defect which was common in all SiC polytypes. Its fingerprints were the characteristic phonon replicas in luminescence spectra. First-principles calculations were performed for the vibrational spectra of various defect complexes, and it was found that C antisite clusters exhibited vibrational modes within the frequency range of the DII spectrum. The clusters possessed very high binding energies which guaranteed their thermal stability. This was a known feature of the DII center. The di-carbon antisite (C2)Si (two C atoms sharing a Si site) was an important building block of these clusters.

Carbon Antisite Clusters in SiC - a Possible Pathway to the DII Center. A.Mattausch, M.Bockstedte, O.Pankratov: Physical Review B, 2004, 69[4], 045322 (5pp)