ROLE OF CLUSTERING IN HYDROGEN TRANSPORT IN SILICON

The effects of H concentration and thermal history on H trapping in hydrogenated amorphous silicon have been investigated through analysis of deuterium diffusion profiles. Unexpected results indicate that the number of traps increases with H concentration while the trap depth increases upon annealing. H equilibrated within the film is associated with traps while rapidly introduced H is not. The results are consistent with a model of trapping and release from H clusters which nucleate and grow in response to added H. It is proposed that the effective diffusion coefficients for high concentrations of H in all forms of Si, amorphous, polycrystalline, and crystalline, are determined by these clusters.