We report the fabrication of a near-infrared avalanche photodetector with a gain-bandwidth product of over 300 GHz. The detector uses a Si multiplication layer and an InGaAs absorption layer. A 3 dB bandwidth of over 9 GHz was measured for current gains as high as 35. Photocurrent measurements using 1.3&mgr;m light indicate a quantum efficiency for the detector of 0.60, near the limit expected based on the absorber thickness. ©1997 American Institute of Physics.