Hydrogen-defect interactions in Si

The interactions between hydrogen and intrinsic defects in silicon are studied using ab-initio (tight-binding) molecular-dynamics simulations in supercells and ab-initio Hartree-Fock in clusters. The configurations, electronic structures, and binding energies of H bound to small vacancy aggregates are calculated. The vacancy (V) and the self-interstitial (I)—both rapid diffusers in Si—efficiently dissociate interstitial H2 molecules. At low temperatures, this results in the formation of {V, H, H} or {I, H, H} complexes. At high temperatures, one or both H’s may be released as interstitials. Preliminary calculations show that H2* result from the reaction {I, H, H}+V→H2*.