Patent ID: 7816866

Claim:
A semiconductor photocathode comprising: a transparent substrate; a first electrode, formed on the transparent substrate and enabling passage of light that has been transmitted through the transparent substrate; a light absorbing layer comprised of a compound semiconductor, formed on the first electrode and in which photoelectrons are excited in response to the incidence of light; a window layer, interposed between the first electrode and the light absorbing layer and being formed of a semiconductor material that is wider in energy band gap than the light absorbing layer, and is lattice matched to the light absorbing layer, wherein a total thickness of the window layer between the first electrode and the light absorbing layer is no less than 10 nm and no more than 200 nm; an electron emission layer, formed on the light absorbing layer, formed of a semiconductor material that is lattice matched to the light absorbing layer, and emitting the photoelectrons excited in the light absorbing layer to the exterior from a surface; and a second electrode, formed on the electron emission layer, wherein the electron emission layer comprises a plurality of openings, the plurality of openings is made no less than 100 nm and no more than 100000 nm in line width, and is made no less than 100 nm and no more than 100000 nm in pitch.