Nitrogen-vacancy complexes in SiC - Final annealing products of the silicon vacancy?

It is commonly accepted that the silicon vacancy (V-Si) in SiC anneals out at temperatures above 750degreesC. The annealing process, however, is not well understood and possible annealing products like CSiVC and VSiNC-pairs would be still electrically active. Thus, further annealing steps are required and are indeed observed at temperatures around 1050degreesC and 1400degreesC. In this theoretical work, we show these annealing stages to be explained by a successive migration of N-atoms towards vacancies forming V-Si(N-C)n-complexes. Like the B-center (VN4) in diamond, the fully nitrogen passivated vacancy V-Si(N-C)(4) is electrically and optically inactiv. Therefore this stable complex (10 eV binding energy) is an ideal candidate for a final annealing product of the silicon vacancy in SiC.