The authors report on the design, characterization, and performance of silicon-rich SiGe waveguide photodetectors grown directly on silicon without virtual buffer relaxation layers. The type-II band offsets of the SiGe system is used to engineer a "W-structure" for absorption at 1.3 mu m. Multimode waveguide devices are found to have a responsivity of 13.2 mA/W and a specific detectivity of 1.8 X 10(8) cm Hz(1/2) W-1 at 1.3 mu m. Variation in the responsivity versus length of single-mode waveguide devices was used to characterize the material, yielding an optical absorption coefficient of 11.21 cm(-1) for a single active region that is 25 angstrom thick. The 500 mu m long single-mode devices exhibit a 3 dB bandwidth of 1.54 GHz. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3039688]