A photodiode has an absorption layer and a cap layer operatively connected to the absorption layer. A pixel is formed in the cap layer and extends into the absorption layer to receive charge generated from photons therefrom. The pixel defines an annular diffused area to reduce dark current and capacitance. A photodetector includes the photodiode. The photodiode includes an array of pixels formed in the cap layer. At least one of the pixels extends into the absorption layer to receive charge generated from photons therefrom. At least one of the pixels defines an annular diffused area to reduce dark current and capacitance.