Amorphous Si0.87Ge0.13 is deposited on n-Si (100) substrate by ion beam sputtering (IBS) and doped through thermal diffusion of phosphorus to fabricate n-poly-Si0.87Ge0.13 thin film. The formation of Schottky junction is made by deposition Ni on n-poly-Si0.87Ge0.13 by IBS. Solid-phase reaction mainly occurred above 400℃ by rapid thermal annealing at the interface of Ni/n-poly-Si0.87Ge0.13. Phase identification and depth profile were investigated by X-ray diffraction (XRD) and Auger electron spectroscopy (AES), respectively. The electrical properties of both unannealed and annealed Ni/n-poly-Si0.87Ge0.13 were studied by current-voltage (I-V) measurement. The results demonstrate that the Schottky barrier height (SBH) changes little with the annealing temperature between 300 and 600℃. The constancy of SBH is attributed to the properties of the interface itself which determine the SBH and substantially independent of whether the interfacial material is nickel or nickel germanosilicide.