ROLE OF CLUSTERING IN HYDROGEN TRANSPORT IN SILICON

The effects of H concentration and thermal history on H trapping in hy drogenated amorphous silicon have been investigated through analysis o f deuterium diffusion profiles. Unexpected results indicate that the n umber of traps increases with H concentration while the trap depth inc reases upon annealing. H equilibrated within the film is associated wi th traps while rapidly introduced H is not. The results are consistent with a model of trapping and release from H clusters which nucleate a nd grow in response to added H. It is proposed that the effective diff usion coefficients for high concentrations of H in all forms of Si, am orphous, polycrystalline, and crystalline, are determined by these clu sters.