We describe the fabrication and characterization of silicon-on-insulator, p+-i-n+ waveguide photodetectors with enhanced sensitivity to wavelengths around 1550nm. Increased sensitivity to sub-band-gap light results from the deliberate introduction of mid-band-gap defects via 1.5MeV silicon-ion implantation to a dose of 1×1012cm−2. For a waveguide of length of 6mm, an on-chip signal of 3.5dBm generates a photocurrent of 5μA while the defect-induced excess optical absorption is 8dB. Postimplantation annealing at a temperature of 300°C for 10min increases the photocurrent to 19μA, corresponding to a responsivity of 9mA∕W, while reducing the excess loss to 2dB. The devices described here are completely compatible with standard silicon processing and can be integrated easily with other photonic and electronic functionalities on the same silicon substrate.