US Patent 10901150 Metal contact free photodetector with sidewall doping

A metal-contact-free photodetector includes an optically absorbing material, e.g. germanium, mounted on a device layer of a photonic integrated circuit, which includes a p-type contact and an n-type contact on opposite sides of a waveguide. The contacts are comprise of a plurality of independently doped regions ranging from lowest doped adjacent the waveguide to highest doped remote from the waveguide. An additional element is to add p and/or n doping on one or more of the sidewalls of the optically absorbing material, e.g Germanium. The advantage compared to the previously disclosed metal-contact-free photodetectors is that the bandwidth is much higher, and full speed is attained at lower voltage.