Photosensor having impurity concentration gradient

摘要

A photosensor including a transparent electrode for transmitting incident light and a photoconductive layer receiving light from the transparent electrode for performing photoelectric conversion, is disclosed in which the photoconductive layer is made of amorphous silicon, the amorphous silicon contains 5 to 30 atomic percent hydrogen and is doped with at least one selected from elements belonging to the groups II and III in such a manner that a region remote from the transparent electrode is higher in the concentration of the selected element than another region proximate to the transparent electrode, and a voltage is applied across the photoconductive layer so that a surface of the photoconductive layer facing the transparent electrode is at a positive potential with respect to another surface of the photoconductive layer opposite to the surface facing the transparent electrode.