STRUCTURAL AND ELECTRICAL-PROPERTIES OF N-TYPE POLY-SI FILMS PREPARED BY LAYER-BY-LAYER TECHNIQUE

Polycrystalline silicon (poly-Si) films have been prepared from fluorinated precursors by introducing a layer-by-layer technique into hydrogen-radical-enhanced chemical vapour deposition (HR-CVD). The degradation in crystallinity caused by phosphine doping was found to be compensated by this novel technique and a highly ordered structure with a strong (220) orientation was observed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The hydrogen was efficiently removed from the growing film and marked evolution of the SiH(n) stretching mode was observed in IR absorption measurements. The measurements of dark conductivity showed that the carrier conduction at room temperature was dominated by a process of thermionic emission over grain boundary barriers. The trapping states as well as the recombination centres at the grain boundary of the growing film were passivated with the aid of atomic hydrogen, and the resulting films showed higher photoconductivity with the etamutau product of around 10(-4) cm2 . V-1.