Epitaxial Silicon Avalanche Photodiodes for Single Photon Detection with Picosecond Resolution

Silicon avalanche photodiodes, designed to operate at bias higher than the breakdown voltage, have been fabricated in a p epitaxial layer over a p++ substrate. The device structure was designed to obtain ultrafast detection of single optical photons, as required in applications such as optical fiber testing, laser ranging, etc. Experiments demonstrate a time resolution having 45 picoseconds full-width at half maximum and carrier diffusion effects remarkably lower than previous non-epitaxial devices.