Ni-seeding effects on the properties of polycrystalline silicon–germanium grown at low temperature

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We have investigated the Ni-seeding effects on the low-temperature growth of the polycrystalline silicon–germanium (poly-SixGe1−x) films by reactive thermal chemical vapor deposition with Si2H6 and GeF4. Very thin Ni films (<2 nm) were deposited on the glass substrates by electron beam evaporation in prior to poly-SixGe1−x deposition. The crystallinity and electrical performance of the poly-SixGe1−x films were characterized. p-channel bottom-gate thin-film transistors (TFTs) were also fabricated with these films to evaluate the effect of Ni seeding on device performance. We found that a certain amount of Ni, i.e., less than 0.5 nm, impacts upon the grain size and crystallinity without additional degradation of electrical properties due to the incorporation of Ni in the film. A 0.2 nm equivalent thickness of Ni gives the best crystallinity and the largest grain size (135 nm) and results in the highest mobility (31 cm2/V s) in p-channel TFTs fabricated on SiO2/Si substrates.