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

Abstract

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 vacancy-related centers in irradiated 3C-SiC and 4H-SiC and semi-insulating 4H-SiC are interpreted in terms of the proposed hierarchy of annealing mechanisms.