A comparison of microcrystalline silicon prepared by plasma-enhanced chemical vapor deposition and hot-wire chemical vapor deposition: electronic and device properties

Abstract

The optoelectronic properties of undoped μc-Si : H have been investigated, with emphasis on the states close to the edges of the band gap. The usefulness of the constant photocurrent method (CPM) for the determination of the absorption coefficient, α(E), is critically described. Combined with carefully evaluated photothermal deflection spectroscopy data, CPM spectra yield valuable information on the transport and dynamics of photo-generated carriers. By comparing photoluminescence and Raman spectra on high-quality samples prepared by plasma-enhanced and hot-wire chemical vapor deposition, with different silane concentrations in the gas stream, a correlation between the microstructure and photoluminescence energy is obtained. It is proposed that the density of band tail states is reduced with increasing silane concentration, leading to an increase in the photoluminescence energy and in the open-circuit voltages of solar cells.