PURPOSE: To greatly increase the quantum efficiency of photoelectric surface of semiconductor by forming a light reflection film on the rear side of crystallized substrate, or forming the film on the rear side of a transparent substrate disposed being in contact with the rear face of the substrate.

CONSTITUTION: The remaining light not absorbed by an active layer 12 enters a crystallized substrate 10 passing through the layer 12, and reaches a light reflection film 14 formed on the rear face, and then after being reflected there arrives at the layer passing through the substrate again. Since the substrate 10 has a transmission ratio of 99% or more substantially with respect to the light having the wavelength passed through the layer 12 and only the slight light is reflected at the face reaching the substrate 10 from the layer 12, the light passed through the layer 12 is almost reflected against a light reflection film 14 and returns to the layer 12 again. The light returned to the layer 12 generate photoelectrons, which are discharged into vacuum from a photoelectric surface 16.