Study of metastabilities in microcrystalline silicon films by photoconductivity techniques

We present a characterisation of the photoelectronic properties of a series of microcrystalline silicon samples which were deposited by hot-wire chemical vapour deposition and had a range of crystallinity from high-crystalline volume fraction to amorphous nature. Samples were characterised by dark and photocurrent measurements and by application of the steady-state photocarrier grating technique. Similarities exist for the temperature-dependent photoconductivity between microcrystalline silicon and hydrogenated amorphous silicon samples with respect to the observation of thermal quenching on the one hand side and its absence for samples, more n-type in character, on the other hand side. The minority carrier diffusion length of the microcrystalline samples does hardly change with temperature which indicates a steeper distribution of valence band tail states. We also cover metastability issues with respect to changes in the conductive properties upon light-induced degradation and exposure to air or water.