The effect of mixing hydrogen with silane on the electronic and optical properties of hydrogenated amorphous silicon thin films

Abstract

The electronic and optical properties of a-Si:H films prepared by the r.f. glow discharge method from a mixture of SiH₄ and H₂ were studied. The effects of variation in the concentration of H₂ in the mixture were also investigated. The dark conductivity of a-Si:H films reaches a minimum at a low concentration of H₂ and then increases with increasing concentration of H₂. In addition, the photoconductive gain shows a maximum at a low concentration of H₂. The band gap, however, remains virtually constant up to 25% H₂ and then increases significantly as the H₂ concentration is increased further. The activation energy increases slowly with H₂ concentration up to 25% and then decreases with a further increase in the H₂ concentration. IR vibrational spectra show an increase in the amount of Si-H bonding as the H₂ concentration increases to 25% and then a decrease with a further increase in the H₂ concentration.