Single hydrogen defects and hydrogen dimers in Si
R Jones & B. Hourahine
School of Physics, The University of Exeter, Exeter EX4 4QL, U.K.
The behaviour of hydrogen in many semiconductors is still unexplored but is best understood in Si. DLTS measurements show that isolated H can be a donor which diffuses rapidly at low temperatures and is subsequently trapped by other defects. Several defects consisting of a single hydrogen atom and another impurity are known such as complexes with carbon or oxygen. These impurities have been thought to simply perturb the electronic structure of H. However, recent combined Laplace DLTS and theoretical studies, to be described, have shown that in the case of carbon this is not the case and we find that the electrical properties of carbon-hydrogen pairs are surprisingly different from those of isolated H .
One possible product of the anneal of H is a hydrogen dimer which as a molecule has been found theoretically to be exceptionally stable although evidence for its existence has been hard to come by. The recent observations by infra-red absorption of modes attributed to hydrogen molecules has led to a considerable debate. Here we discuss the origin for this activity and investigate in detail the possible IR-transitions.
 O. Andersen, L. Dobaczewski, A. R. Peaker, K. Bonde Nielsen, B. Hourahine, R. Jones, P. R. Briddon, S. Oberg, Phys. Rev. B, in press