It was recalled that the hydrogenated amorphous material was a structure-sensitive non-equilibrium semiconductor and that, even in its exclusively intrinsic state, a very large variety of defects could be frozen-in during preparation. Attention was paid here to the use of SiH4 glow discharge plasma-deposition methods in reducing the defect content. It was noted that the plasma comprised numerous ions, radicals and neutral species, as well as electrons. Within the plasma, various secondary chemical reactions took place and resulted in the formation of various species. The less reactive and long-lived SiH3 radical exhibited a high surface diffusion coefficient, and was most favorable to the growth of a less strained and high density network. It was noted that H could terminate a Si dangling bond, could contribute a high surface diffusion coefficient to the precursors by its coverage of the growing surface, and could stabilize broken Si-Si bonds by passivating the created dangling bonds. It could also permit re-formation of the rigid Si-Si bond via its out-diffusion from the network.

D.Das: Solid State Phenomena, 1995, 44-46, 227-58