The interstitial and vacancy mediated B diffusion in silicon carbide was investigated with an ab initio method. The B interstitials in p-type and n-type materials were found to be far more mobile than the B-vacancy complexes. A kick-out mechanism and an interstitialcy mechanism govern the diffusion in p-type/intrinsic and n-type material, respectively. A comparison of activation energies demonstrated that the equilibrium diffusion was dominated by the positive hexagonal interstitial for typical experimental conditions. The activation energy and the charge state was in agreement with experimental findings. The analysis of the kick-out reaction demonstrated that Si and C interstitials have different effects on B acceptors on the Si and C sub-lattice (BSi and BC). While Si interstitials mediate the diffusion of both acceptors, C interstitials were only relevant for BC. A larger kick-in barrier into Si sites was found than into C sites. This implied a dominant formation of BC in the extended diffusion tails of B profiles. The stable B complexes with C or B interstitials were found that potentially reduced B diffusion. This, and the characteristics of the kick-out mechanism, helped to explain recent co-implantation experiments.

Different Roles of Carbon and Silicon Interstitials in the Interstitial-Mediated Boron Diffusion in SiC. M.Bockstedte, A.Mattausch, O.Pankratov: Physical Review B, 2004, 70[11], 115203 (13pp)

Diffusivity of C and Si in SiC