Effect of Filament Bias on the Properties of Amorphous and Nanocrystalline Silicon from Hot-Wire Chemical Vapor Deposition

ABSTRACTAt the high temperatures during hot-wire assisted chemical vapor deposition, ther- mal emission of electrons from the filament occurs. We studied the effect of filament bias, and thus the filament-to-substrate current, on the structural, electronic and optical properties of amorphous and nanocrystalline silicon deposited by this method. The current drawn by the substrate can be varied by many orders of magnitude as thermally emitted electrons are increasingly collected with applied bias voltage. The crystallinity of the nanocrystalline samples is not affected by the bias voltage. The defect density in amorphous silicon is affected by the electron bombardment at high bias voltage only, for which we also find a significant reduction in the mobility-lifetime product from steady-state photoconductivity.