In order to determine the mechanism or mechanisms for H transport in a-Si:H one must identify the reactions that bring deeply bonded H (on dangling bonds) to the transport band which was some form of interstitial H. Further, one must have reliable values of the energy difference between these deep states and transport states, as well as the barrier energies between neighboring transport sites. Since experiments clearly showed a dependence of H diffusion activation energy on the charge of the mobile H and on the Fermi level, different charge states for the H must be included. All of these factors were considered in order to obtain an explanation of how H migrated in a-Si:H.

Diffusion of Hydrogen in Different Charge States in Realistic Models of a-Si:H. P.A.Fedders: Physical Review B, 2002, 66[19], 195308 (6pp)