Self-diffusion in Isotopically Enriched Silicon Carbide and Its Correlation with Dopant Diffusion

Diffusion of C13 and Si30 in silicon carbide was performed with isotopically enriched 4H-Si28C12∕natSiC heterostructures which were grown by chemical vapor phase epitaxy. After diffusion annealing at temperatures between 2000°C and 2200°C the Si30 and C13 profiles were measured by means of secondary ion mass spectrometry. We found that the Si and C diffusivity is of the same order of magnitude but several orders of magnitude lower than earlier data reported in the literature. Both Si and C tracer diffusion coefficients are in satisfactory agreement with the native point defect contribution to self-diffusion deduced from B diffusion in SiC. This reveals that the native defect which mediates B diffusion also controls self-diffusion. Assuming that B atoms within the extended tail region of B profiles are mainly dissolved on C sites, we propose that B diffuses via the kick-out mechanism involving C interstitials. Accordingly, C diffusion should proceed mainly via C interstitials. The mechanism of Si diffusion remains unsolved but Si may diffuse via both Si vacancies and interstitials, with the preference for either species depending on the doping level.