EPR and theoretical studies of negatively charged carbon vacancy in 4H-SiC

Abstract

Carbon vacancies (VC) 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 (VC-) 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 VC. First-principles calculations confirm that the HEI1 center arises from VC- at hexagonal sites. The HEI1 spectrum shows a transition between C1h and C3v symmetries due to a fast reorientation effect reflected in the nature of this defect. The photo-EPR data suggest that VC 2- is the dominant form of VC when the Fermi level lies 1.1 eV below the conduction band. © 2005 The American Physical Society.