New Insights into Processes of Hydrogen Incorporation and Hydrogen Diffusion in Hydrogenated Amorphous Silicon

By secondary ion mass spectrometry profiling, the incorporation and the diffusion of hydrogen in undoped plasma-deposited hydrogenated amorphous silicon (a-Si:H) films were studied as a function of hydrogen concentration. The results show that in the range between 1 and 10 at% a structure-related hydrogen solubility limits the hydrogen incorporation. The observed concentration dependence of the hydrogen diffusion coefficient can be explained by a band model of hydrogen diffusion involving a rather mobile hydrogen chemical potential for material of low hydrogen concentration.