The diffusion phenomena in hydrogenated amorphous material were modelled by assuming that mobile H which was excited from Si-H bonds normally annihilated at dangling-bond defects; as in the so-called H-collision model for light-induced metastability. This diffusion model explained the persistent puzzle of the doping dependence of the H diffusion coefficient. It also yielded the magnitudes of the Arrhenius parameters for doped and undoped hydrogenated amorphous material. Mobile H diffused over an energy barrier of about 0.3eV at room temperature. Its diffusion rate was slightly greater than that of H in crystalline Si.

Hydrogen Diffusion and Mobile Hydrogen in Amorphous Silicon H.M.Branz: Physical Review B, 1999, 60[11], 7725-7