High responsivity near-infrared photodetectors in evaporated Ge-on-Si

Germanium is considered the most suitable semiconductor for monolithic integration of near-infrared detectors on silicon photonic chips. Here we report on Ge-on-Si near-infrared photodetectors fabricated by thermal evaporation, demonstrating the use of phosphorus spin-on-dopant to compensate the acceptor states introduced by dislocations. The detectors exhibit 1.55 μm responsivities as high as 0.1 A/W, more than two orders of magnitude larger than in undoped devices and comparing well with state-of-the-art p-i-n photodiodes. This approach enables simple and low-cost monolithic integration of near-infrared sensors with silicon photonics.