Diffusion and Defects in Elementary and Compound Semiconductors
Dopant and self-diffusion in epilayers and isotope heterostructures of silicon carbide (SiC)
Diffusion of 13C and 30Si in silicon carbide was performed with isotopically enriched
4H-28Si12C/natSiC heterostructures which were grown by chemical
vapor phase epitaxy. After diffusion annealing at temperatures between 2000oC and
2200oC the 30Si and 13C 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.
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