We demonstrate a Si-based photodetector with a response in the 1.3-1.55μm wavelength range. The active absorption layer of the pin photodiode consists of a pseudomorphic SiGeC alloy grown on a Si substrate with a Ge content of 55% and a thickness of 800 A. By using a single-mode fiber butt coupled to the waveguide facet, the external quantum efficiency for a 400-gin long waveguide is 0.2% at 1.55μm, and 8% at 1.3 gin. The external efficiency can be further improved by using a multiple layer absorber structure. The high efficiency and high speed characteristics together with the low leakage current density imply potential application of the SiGeC/Si photodetector for optical fiber communications and optical interconnects in the 1.3-1.55μm wavelength range.