EPR and theoretical studies of negatively charged carbon vacancy in 4H-SiC -: art. no. 193202

Carbon vacancies (V-C) are typical intrinsic defects in silicon carbides (SiC) and so far have been observed only in the form of positively charged states in p-type or semi-insulating SiC. Here, we present electron-paramagnetic-resonance (EPR) and photoinduced EPR (photo-EPR) observations of their negatively charged state (V-C(-)) in n-type 4H-SiC. This EPR center (called HEI1) is characterized by an electron spin of 1/2 in a Si-Si antibonding state of V-C. First-principles calculations confirm that the HEI1 center arises from V-c(-) at hexagonal sites. The HEI1 spectrum shows a transition between C-1h and C-3v symmetries due to a fast reorientation effect reflected in the nature of this defect. The photo-EPR data suggest that V-C(2-) is the dominant form of V-C when the Fermi level lies 1.1 eV below the conduction band.