Low-temperature migration of hydrogen and interaction with oxygen

Low-dose proton implantation into n-type silicon below 80 K initiates the formation of two deep donor centres containing hydrogen. The centres, E3' and E3", have been observed by deep-level transient spectroscopy carried out in situ with as-implanted samples. The centres have very similar emission rates, and are discerned only because they form and anneal differently. In the neutral charge state E3' anneals in 10 min. at 100 K while E3" anneals in approximate to 50 ms at 75 K. These anneals lead to the same negatively charged acceptor-type centre from which both E3' and E3" can be recovered: E3' by forward-bias injection, and E3" by exposing the sample to band-gap light. The E3' recovery is associated with fast migration of hydrogen, while E3" recovers instantly without migration. In the positive charge state E3' anneals in the range 200 - 240 K as a result of hydrogen migration and trapping at oxygen, while E3" anneals in a two-step process through E3". The centre for recovery of E3' and E3" anneals in the range 230 - 270 K restrained by hydrogen-oxygen interaction. We discuss the annealing scenario with reference to present understanding of isolated hydrogen in silicon. The previous identification of E3' with bond-centre hydrogen is maintained. We suggest that E3" is a perturbed form of E3' but a definite assignment is not obtained.