The influence of post-hydrogenation on the electrical and optical properties of solid phase crystallized polycrystalline silicon (poly-Si) was examined. The passivation of grain-boundary defects was measured as a function of the passivation time. The silicon dangling-bond concentration decreases with increasing passivation time due to the formation of Si-H complexes. In addition, large H-stabilized platelet-like clusters are generated. The influence of H on the electrical properties was investigated using temperature dependent conductivity and Hall-effect measurements. For poly-Si on Corning glass, the dark conductivity decreases upon hydrogenation, while it increases when the samples are fabricated on silicon-nitride covered Borofloat glass. Hall-effect measurements reveal that for poly-Si on Corning glass the hole concentration and the mobility decrease upon post-hydrogenation, while a pronounced increase is observed for poly-Si on silicon-nitride covered Borofloat glass. This indicates the formation of localized states in the band gap, which is supported by sub band-gap absorption measurments. The results are discussed in terms of hydrogen-induced defect passivation and generation mechanisms.
The origin of the formation of {100} and {111} grain textures in polycrystalline silicon thin films prepared with multiple excimer laser shots at the super-lateral-growth crystallization regime is investigated in this study. Our results demonstrate that the type of texture formed is determined solely by the thickness of the silicon layer. At a critical value of 40 nm, a transition from {100} to {111} texture is observed with increasing layer thickness. It is therefore proposed that below this critical value, the texture formation is governed by surface energy anisotropy whereas above it, the kinetics of the solidification process predominate.
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