The diffusion of interstitial atomic H in 4H-type material 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 lower than 0.6eV. A comparison of this value, with the calculated zero-point vibration energy of interstitial H, indicated that H diffused very rapidly in perfect volumes of the lattice until it became trapped. In p-doped (B,Al) material, dissociation of 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. The latter 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