Photosensor having an amorphous silicon photoabsorption layer

Claim 1

A photosensor for detecting optical radiation, comprising: an insulator layer having an upper major surface and a lower major surface; a first electrode provided on the upper major surface of the insulator layer for collecting first type carriers that are formed upon incidence of optical radiation and having one of first and second polarities, said first electrode having an upper major surface and a lower major surface and segmented into a plurality of pixel electrodes each defined by a side wall, said plurality of pixel electrodes being separated from each other on the upper major surface of the insulator layer by a gap defined by a pair of opposing side walls of adjacent pixel electrodes; a first silicon carbide layer having a lower major surface and an upper major surface and provided on the upper major surface of the insulator layer to bury the plurality of pixel electrodes underneath, said first silicon carbide layer further covering the gap separating adjacent pixel electrodes; an optical absorption layer of amorphous silicon having a lower major surface and an upper major surface and provided on the silicon carbide layer continuously such that the amorphous silicon layer extends over the plurality of pixel electrodes and the gap between adjacent pixel electrodes, said optical absorption layer having a first conductivity and producing the first type carriers and second type carriers upon incidence of the optical radiation, said second type carriers having the other of the first and second polarities; said first silicon carbide layer protecting the optical absorption layer from chemical reaction caused between the optical absorption layer and the first electrode; a second silicon carbide layer having a lower major surface and an upper major surface and provided on the amorphous silicon layer for prohibiting passage of the first type carriers therethrough; and a second electrode of a transparent material having an upper major surface and a lower major surface and provided on the upper major surface of the silicon carbide layer for collecting the second type carriers produced in the optical absorption layer; said first silicon carbide layer being doped to have a second conductivity that enables formation of an electric field equal to or larger than about 4 volts/um in magnitude in the amorphous silicon layer and such that said second conductivity of the first silicon carbide is equal to or smaller than said first conductivity of the amorphous silicon layer.