due to the potential slope and is recombined at relatively lower probability this means that the light having such a shorter wavelength can also contribute to the generation of effective photocurrent like the light having a relatively longer wavelength which reaches the amorphous silicon layer 24 to generate photocarriers therein as described hereinabove the photosensitive device of the present invention develops an improved spectral characteristic with respect to the shorter wavelength for reference since the amorphous silicon layer of the prior art structure shown in fig3 b in comparison to the amorphous silicon layer 26 of this embodiment is relatively deeply doped and thus has a lower resistivity an electric field is barely formed therein consequently even if photocarrier pairs are generated by an incident light 32a they are recombined without flowing through the layer the carrier pairs thus do not contribute to the photocurrent generation as illustrated in fig4 this is also the case when the amorphous silicon layer 26 is of the n type and the amorphous silicon layer 24 is intrinsic i or of the p type the energy band construction in this case is as depicted in fig5 a fig5 b illustrates the band energy structure of the.