A semiconductor substrate doped with a first doping type is positioned adjacent an insulated gate electrode that is biased by a gate voltage. A first region within the semiconductor substrate is doped with the first doping type and biased with a bias voltage. A second region within the semiconductor substrate is doped with a second doping type that is opposite the first doping type. Voltage application produces an electrostatic field within the semiconductor substrate causing the formation of a fully depleted region within the semiconductor substrate. The fully depleted region responds to absorption of a photon with an avalanche multiplication that produces charges that are collected at the first and second regions.