Patent ID: 7129469

Claim:
A photodetector having a MSM (Metal-Semiconductor-Metal) structure, comprising: a substrate; a multilayer film that is disposed over the substrate and includes a low refractive index layer and a high refractive index layer that are alternately laminated as a unit cycle, at least one of the low refractive index layer and the high refractive index layer being a photoabsorption layer composed of semiconductor; a first electrode having a portion embodied in the multilayer film; and a second electrode having a portion embodied in the multilayer film, the portion of the second electrode opposite the portion of the first electrode, the multilayer film being formed such that a wavelength region corresponding to a band edge of a photonic band overlaps at least a part of an absorption band of the photoabsorption layer, thereby delaying a group velocity of incidence light with a predetermined wavelength that belongs to the absorption band of the photoabsorption layer.