Conductance fluctuations in VHF-PECVD grown hydrogenated microcrystalline silicon thin films

Coplanar conductance fluctuations or excess noise of undoped hydrogenated microcrystalline silicon (muc-Si: H) thin films grown by VHF-PECVD from silane-hydrogen mixtures with silane concentrations from 2% to 6% have been studied between room temperature and 470 K. We report that undoped muc-Si: H thin films show similar noise-power spectra to those of undoped a-Si : H films in a coplanar sample geometry. At lower temperatures, the noise with the slope alpha = 0.60 +/- 0.07 and at higher temperatures, the noise with the slope alpha close to unity dominate the spectrum. The noise magnitude decreases with decreasing silane concentration and becomes strongly temperature dependent with increased crystallinity. (C) 2003 Kluwer Academic Publishers