Abstract: A photo-detector for detecting photons generated by a received light is disclosed. The photo-detector includes a semiconductor substrate, two or more guided regions, a photo sensing region, and two or more detection regions. The semiconductor substrate and the guided regions are doped with the first conductive type of dopant. The photo sensing region is disposed between the two or more guided regions for an impinging photon from the received light to generate photo carriers. The detection regions are doped with a second conductive type of dopant. The guided regions are respectively connected to power sources to apply an electric potential across the guided regions for controlling a detectivity of the impinging photon. The photo sensing region is provided to form at least a pn junction between the guided regions that is reverse biased so as to reduce or prevent a leakage path between the guided regions.