The structure of 1.5–2.0 eV band gap amorphous silicon films prepared by chemical annealing

Structural properties of band gap tuned (1.5–2.0 eV) hydrogenated amorphous silicon were investigated. The short range order associated with the local silicon–silicon bonding was measured by X-ray, Raman spectroscopy, optical absorption spectrum and weight density analysis. The atomic size and/or the distance between nearest neighbor silicon atoms did not appear to change as a function of the hydrogen content or the band gap. The short range order, the silicon bond length and bond angle distributions, were invariant as the band gap varies from 1.5–2.0 eV. Other structural properties were also investigated. The hydrogen thermal desorption spectrum and the infra-red absorption spectrum were also measured. While, the hydrogen evolves from largest amount of hydrogen and/or high Si–H2 content materials at lower temperatures, this feature is not correlated with the band gap. The band gap was strongly correlated to the Si–H2 density determined by the infra-red absorption analysis (correlation coefficient >0.92).