First-principles calculations were carried out on models for the Z1/Z2 defects in 4H–SiC which were found in as-grown and irradiated n-type material. It was shown that an interstitial-N–interstitial-C defect was exceptionally thermally stable, bistable, and had negative-U character with donor and acceptor levels close to those attributed to the defect.

Z1/Z2 Defects in 4H–SiC. T.A.G.Eberlein, R.Jones, P.R.Briddon: Physical Review Letters, 2003, 90[22], 225502 (3pp)