Annealing of multivacancy defects in 4H-SiC

The annealing behavior of defects observed in electron paramagnetic resonance (EPR) and photoluminescence (PL) is discussed. We consider the divacancy (the P6/P7 EPR centers) and a previously unreported EPR center that we suggest is a VC - VSi - VC trivacancy and their relationship with each other and with the UD1-3 series of PL lines near 1 eV. We observe that the divacancy and the UD2 PL lines annealing behavior is strongly correlated further establishing the relationship between the EPR and PL centers. We present a detailed discussion of this center and its Si29 and C13 hyperfine spectra which supports our assignment as a trivacancy. The intensity of this center increases with annealing temperature as the divacancy decreases and there is a sample-to-sample correspondence between the overall intensities of the two centers. However, the details of their annealing suggest a more complex relationship than a simple one-to-one transformation. In addition, while the UD1 PL increases with annealing temperature, sample-to-sample variations indicate it is not related to this EPR center.