A device that detects single optical and radiation events and that provides improved blue detection efficiency and lower dark currents than prior silicon SSPM devices. The sensing element of the devices is a photodiode that may be used to provide single photon detection through the process of generating a self-sustained avalanche. The type of diode is called a Geiger photodiode or signal photon-counting avalanche diode. A CMOS photodiode can be fabricated using a “buried” doping layer for the P-N junction, where the high doping concentration and P-N junction is deep beneath the surface, and the doping concentration at the surface of the diode may be low. The use of a buried layer with a high doping concentration compared to the near surface layer of the primary P-N junction allows for the electric field of the depletion region to extend up near the surface of the diode. With a low doping concentration through the bulk of the diode, the induced bulk defects are limited, which may reduce the dark current. The resulting structure provides a diode with improved quantum efficiency and dark current.