Ab initio study of the annealing of vacancies and interstitials in cubic SiC: Vacancy-interstitial recombination and aggregation of carbon interstitials

The annealing kinetics of mobile intrinsic defects in cubic SiC is investigated by an ab initio method based on density-functional theory. The interstitial-vacancy recombination, the diffusion of vacancies, and interstitials to defect sinks ~e.g., surfaces or dislocations! as well as the formation of interstitial clusters are considered. The calculated migration and reaction barriers suggest a hierarchical ordering of competing annealing mechanisms. The higher mobility of carbon and silicon interstitials as compared to the vacancies drives the annealing mechanisms at lower temperatures including the vacancy-interstitial recombination and the formation of interstitial carbon clusters. These clusters act as a source of carbon interstials at elevated temperatures. In p-type material the transformation of the silicon vacancy into the more stable vacancy-antisite complex constitutes an annealing mechanism which is activated before the vacancy migration. Recent annealing studies of vacancyrelated centers in irradiated 3C-SiC and 4H-SiC and semi-insulating 4H-SiC are interpreted in terms of the proposed hierarchy of annealing mechanisms.