Highly sensitive charge-coupled photodetector including an electrically isolated reversed biased diffusion region for eliminating an inversion layer

Claim 1

A low capacitance charge-coupled semiconductor photodiode structure comprising, a semiconductor substrate layer of one conductivity type, a diffusion region of opposite conductivity type disposed in the surface of said substrate, the area of said diffusion region being substantially smaller than the area of said substrate surface, a first insulating layer disposed on said substrate surface exclusive of said area of said diffusion region, a layer of gate material disposed on the surface of said first insulating layer which in combination with said substrate layer forms a photodiode, a second insulating layer disposed on the surface of said gate layer and the surface of said diffusion region, a first electrically conductive contact extending through said second insulating layer to connect an output device to a portion of the surface of said diffusion region, a second electrically conductive contact for connecting a controllable bias voltage means to said layer of gate material for biasing said diffusion region positive to eliminate any inversion layer at the interface of said first insulating layer and said substrate and electrically isolating said diffusion region from said photodiode formed by said gate material and said first insulating layer, said photodiode being responsive to light radiation directed on said surface of said second insulating layer to generate charge carriers proportional to said light, said charge carriers being collected by said diffusion region to produce an electrical output signal on said first contact representative of said light radiation.