Interstitial H and H2 in SiC

The properties of hydrogen in 3C and 4H type silicon carbide (SiC) are studied theoretically at the density functional level. We find that only singly positive or negative charge states of hydrogen are thermodynamically stable in SiC. The transition from the positive to the negative charge state (+/-) is at 0.9 and 1.3 eV above the valence band maximum in 3C and 4H structures, respectively. The diffusion barrier for the proton is 0.5 eV (being, however, anisotropic in 4H). For the negative H- the diffusion barrier is found to be considerably higher, of the order of 3 eV.(C) 2003 American Institute of Physics.