It was recalled that C vacancies (VC) were typical intrinsic defects in silicon carbides and had so far been observed only in the form of positively charged states in p-type or semi-insulating SiC. Here, electron-paramagnetic-resonance and photo-induced electron paramagnetic resonance observations were made of their negatively charged state (VC-) in n-type 4H-SiC. This electron paramagnetic resonance center (called HEI1) was characterized by an electron spin of 1/2 in a Si-Si anti-bonding state of VC. First-principles calculations confirmed that the HEI1 center arose from VC- at hexagonal sites. The HEI1 spectrum exhibited a transition between C1h and C3v symmetries due to a fast reorientation effect reflected in the nature of this defect. The photo-electron paramagnetic resonance data suggested that VC2- was the predominant form of VC when the Fermi level lay 1.1eV below the conduction band.

EPR and Theoretical Studies of Negatively Charged Carbon Vacancy in 4H-SiC. T.Umeda, Y.Ishitsuka, J.Isoya, N.T.Son, E.Janzén, N.Morishita, T.Ohshima, H.Itoh, A.Gali: Physical Review B, 2005, 71[19], 193202 (4pp)