It was shown that the multiple trapping of H atoms at shallow acceptors during plasma hydrogenation could explain various features of the resultant H diffusion profile. In the case of heavily-doped p-type material, a plateau in the H profile at the acceptor concentration was preceded by a high concentration plateau near to the surface. It was demonstrated that the plateau could be explained by the successive aggregation of H atoms at acceptors, and that the multiple trapping process appeared to terminate after the agglomeration of 8 to 12 H atoms. The reaction cross-section for multiple trapping was much smaller than that for the first capture, and this behavior was consistent with the ionic capture of H+ at acceptors, followed by neutral multiple capture. It was suggested that the formation of H dimers, which predominated in high-resistivity material, might still be important with regard to the high-concentration near-surface profiles which were seen in heavily-doped samples.

J.T.Borenstein, J.W.Corbett, S.J.Pearton: Materials Science Forum, 1992, 83-87, 51-6