Effect of Hydrogen Dilution of Silane in Hydrogenated Amorphous Silicon Films Prepared by Photochemical Vapor Deposition

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Abstract
Hydrogenated amorphous silicon (a-Si:H) films were prepared by mercury photosensitized decomposition of silane-hydrogen (or-helium) gas mixtures. In hydrogen dilution, a-Si:H films were deposited from 20-100% of the silane fraction and hydrogenated amorphous-microcrystalline mixed-phase silicon (µc-Si:H) films were deposited for less than 10% of the silane fraction. The Si-H2 bond density and optical gap for a-Si:H films increased upon decreasing the silane fraction. The preferential orientation of the crystallites in µc-Si:H films was greatly changed by the silane fraction. However, the film characteristics did not change upon helium dilution. It was found that the hydrogen radical plays a significant role in the film-deposition process. Large-grain-size µc-Si:H films have been obtained, as compared with the grain size for films made by the conventional glow-discharge technique.
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