An analysis was made of the defect-pool model, for the calculation of the density of electronic gap states in hydrogenated amorphous material, that was based upon the equilibration of elemental chemical reactions that involved the separate release and capture of H. A description was given of the corresponding H density of states, and of the distribution of H binding energies, and it was shown that the 2 densities of states were entirely consistent. The H could be captured into weak Si-Si bonds, which could be occupied by one or two H atoms. These were the predominant chemical reactions which controlled the defect density. It was noted that the effective H correlation energy was variable; being negative for most sites, but positive where most defects occurred. It was shown that the electronic density of states reproduced the main features of an earlier defect-pool model; with more charged defects than neutral defects in intrinsic amorphous Si. The electronic density of states and the corresponding H density of states were consistent with a wide range of experimental results, including hydrogenation-dehydrogenation and H diffusion.

M.J.Powell, S.C.Deane: Physical Review B, 1996, 53[15], 10121-32