The Self-Trapping of Hydrogen in Semiconductors

Recent theorectical calculations are discussed which show that the minimum energy site for hydrogen in silicon is the bond-centered site, while a secondary minimum is at the anti-bonding site. It is noted that these are strongly dependent on the relaxation experienced by the silicon atoms neighboring the hydrogen. Several experimental results are discussed, namely, the observed model of the hydrogen-passivated acceptor, etching of the silicon surface by hydrogen, the exponential depth dependence of the near-surface hydrogen diffusion profile and related muonium results, and from these results it is argued that, in some instances at least, the BC-site is the lowest energy site for hydrogen.