The diffusion of interstitial atomic H in 4H-SiC was investigated theoretically, by using the local density approximation of density functional theory. It was found that the diffusion barrier in the perfect crystal was less than 0.6eV. Comparing this value with the calculated zero-point vibration energy of interstitial H indicated that H diffused very rapidly in perfect portions of the SiC lattice, until it became trapped. In p-doped (B, Al) material, dissociation of the H-acceptor complexes was the limiting step in diffusion, with a calculated dissociation energy of 2.5 and 1.6eV for B+H and Al+H, respectively. In irradiated material, the trapping and de-trapping of H by Si vacancies determined the effective diffusion barrier, which lay between 4.0 and 5.3eV; depending upon the Fermi level in p-type and weakly n-type material.

Diffusion of Hydrogen in Perfect, p-Type Doped, and Radiation-Damaged 4H-SiC. B.Aradi, P.Deák, A.Gali, N.T.Son, E.Janzén: Physical Review B, 2004, 69[23], 233202 (4pp)