Patent ID: 8766188

Claim:
A photoconductive element for performing at least one of generation and detection of terahertz radiation, comprising: a photoconductive layer configured to generate photoexcited carriers by being irradiated with excitation light; and a plurality of electrodes provided on the photoconductive layer, wherein the material of the photoconductive layer is a material that makes a depletion layer produced in the photoconductive layer have a thickness smaller than an optical absorption length of the photoconductive layer for a wavelength of the excitation light, wherein the material of the photoconductive layer is a material in which the thickness W of the depletion layer produced in the photoconductive layer is represented by W=(2∈V bi /en) 0.5 , where ∈ denotes a dielectric constant of the photoconductive layer, Vbi denotes a built-in potential on a surface of the photoconductive layer, e denotes an elementary charge, and n denotes a carrier density of the photoconductive layer, wherein a film thickness of the photoconductive layer is selected to the thickness W of the depletion layer within at least a portion of the photoconductive layer between the plurality of electrodes, and wherein the material of the photoconductive layer is a low-temperature-grown compound semiconductor including three or more elements.