Experiments demonstrated that H migration in hydrogenated amorphous material was controlled by the concentration of electronic carriers. Therefore, it was strongly suppressed when the carriers were removed by an electric field. The few H atoms which migrated in a region that was depleted of carriers had a longer mean free path for diffusion; due to a reduction in the concentration of trapping centers. The latter were probably Si dangling bonds.

P.V.Santos, N.M.Johnson: Applied Physics Letters, 1993, 62[7], 720-2