First-principles investigations of Fe-H interactions in silicon

Hydrogen trapping at defects in semiconductors often affects their electrical activity. In particular, H passivates many deep-level defects. In this paper, we study the interactions between interstitial H and the simplest Fe-related defects in Si, namely interstitial iron (Fe_i), substitutional iron (Fe_s) and the interstitial-substitutional iron-boron pair (Fe_iB_s). Our first-principles spin-density-functional calculations are performed in periodic supercells with atomic-like basis sets. The configurations, binding energies, charge and spin states, and vibrational spectra are calculated. The approximate positions of the acceptor and donor gap levels are predicted using the marker method. We show that neither the Fe_iH pair nor the Fe_sH_n complexes are passivated, and that H displaces Fe_i from the Fe_iB_s pair.