Abstract: A photodetection element includes an N-type silicon layer formed in a single crystal state, a P-type germanium-containing layer formed in a polycrystal state and forming a hetero PN junction between the germanium-containing layer and the silicon layer, a first electrode electrically connected to the silicon layer, and a second electrode electrically connected to the germanium-containing layer.

Abstract: A photodetection element is a photodetection element having an incidence surface for light on a back surface of a semiconductor layer, and includes a periodic nano-concave/convex structure provided on a front surface of the semiconductor layer and having convex portions and concave portions constituting a longitudinal resonator and a transverse resonator for the light incident from the incidence surface, the periodic nano-concave/convex structure converting the light into surface plasmons, and a metal film provided to cover the periodic nano-concave/convex structure, a height and an arrangement pitch of the convex portions in the periodic nano-concave/convex structure are set such that a resonance wavelength of the longitudinal resonator and a resonance wavelength of the transverse resonator match, and a thickness of the metal film is equal to or greater than 20 nm.

Abstract: A photodetection element includes a semiconductor layer having, on one surface side, a periodic concave/convex structure that includes periodic convex portions and concave portions and converts light into surface plasmon, and a metal film provided on the one surface side of the semiconductor layer in correspondence to the periodic concave/convex structure, and in the periodic concave/convex structure, a Schottky junction portion that has a Schottky junction with the metal film is provided on a base end side of the convex portion, and a non-Schottky junction portion that does not have a Schottky junction with the metal film is provided on a distal end side of the convex portion.

Abstract: A photodetection element includes a semiconductor layer having, on one surface side, a periodic concave/convex structure that includes periodic convex portions and concave portions and converts light into surface plasmon, and a metal film provided on the one surface side of the semiconductor layer in correspondence to the periodic concave/convex structure, and in the periodic concave/convex structure, a Schottky junction portion that has a Schottky junction with the metal film is provided on a base end side of the convex portion, and a non-Schottky junction portion that does not have a Schottky junction with the metal film is provided on a distal end side of the convex portion.

Abstract: A photodetection element is a photodetection element having an incidence surface for light on a back surface of a semiconductor layer, and includes a periodic nano-concave/convex structure provided on a front surface of the semiconductor layer and having convex portions and concave portions constituting a longitudinal resonator and a transverse resonator for the light incident from the incidence surface, the periodic nano-concave/convex structure converting the light into surface plasmons, and a metal film provided to cover the periodic nano-concave/convex structure, a height and an arrangement pitch of the convex portions in the periodic nano-concave/convex structure are set such that a resonance wavelength of the longitudinal resonator and a resonance wavelength of the transverse resonator match, and a thickness of the metal film is equal to or greater than 20 nm.

Abstract: A photodetector 1A comprises a multilayer structure 3 having a first layer 4 constituted by first metal or first semiconductor, a semiconductor structure layer 5 mounted on the first layer 4 and adapted to excite an electron by plasmon resonance, and a second layer 6 mounted on the semiconductor structure layer 5 and constituted by second metal or second semiconductor.

Abstract: A photodetector 1A comprises an optical element 10, having a structure including first regions and second regions periodically arranged with respect to the first regions along a plane perpendicular to a predetermined direction, for generating an electric field component in the predetermined direction when light is incident thereon along the predetermined direction; and a semiconductor multilayer body 4 having a quantum cascade structure, arranged on the other side opposite from one side in the predetermined direction with respect to the optical element, for producing a current according to the electric field component in the predetermined direction generated by the optical element 10; while the quantum cascade structure includes an active region 4b for exciting an electron and an injector region 4c for transporting the electron, the active region 4b being formed on the outermost surface on the one side of the injector region 4c in the quantum cascade structure.

Abstract: A photodetector 1A comprises an optical element 10, having a structure including first regions and second regions periodically arranged with respect to the first regions along a plane perpendicular to a predetermined direction, for generating an electric field component in the predetermined direction when light is incident thereon along the predetermined direction; arid a semiconductor multilayer body 4 having a quantum cascade structure, arranged on the other side opposite from one side in the predetermined direction with respect to the optical element, for producing a current according to the electric field component in the predetermined direction generated by the optical element 10; while the quantum cascade structure includes an active region 4b having a first upper quantum level and a second upper quantum level lower than the first upper quantum level, and an injector region 4c for transporting an electron excited by the active region 4b.

Abstract: A photodetector 1A comprises an optical element 10A for generating an electric field component in a predetermined direction when light is incident thereon along the predetermined direction, the optical element 10A having a structure including first regions and second regions periodically arranged with respect to the first regions along a plane perpendicular to the predetermined direction; and a semiconductor layer 40, arranged on the other side opposite from one side in the predetermined direction with respect to the optical element 10A, having a semiconductor multilayer body 42 for generating a current according to the electric field component; each end part on the other side of the second regions being located closer to the other side than is each end part on the other side of the first regions; each first region being made of a dielectric body having a refractive index greater than that of each second region.

Abstract: An optical element 10 for transmitting light therethrough along a predetermined direction and modulating the light comprises a structure 11 having a first region R1 and a second region R2 periodically arranged with respect to the first region R1 along a plane perpendicular to the predetermined direction, the first and second regions R1, R2 having respective refractive indexes different from each other, and properties of transmitting the light therethrough.

Abstract: A photodetector 1A comprises a multilayer structure 3 having a first layer 4 constituted by first metal or first semiconductor, a semiconductor structure layer 5 mounted on the first layer 4 and adapted to excite an electron by plasmon resonance, and a second layer 6 mounted on the semiconductor structure layer 5 and constituted by second metal or second semiconductor.

Abstract: In a terahertz antenna module 1, a photoconductive antenna element 17 is fixed to a wiring board 9, and electrically connected to an electric signal input/output pin 24 of an electric signal input/output port 23 via a signal electrode of the wiring board 9. Further, a buffer member 7, a hemispherical lens 8, a photoconductive antenna element 17, and the wiring board 9 are disposed in a recess 3 of a container 2 in this order from an opening 6 side of the container 2, and by attaching a cover 25 to the container 2, the wiring board 9, the photoconductive antenna element 17, and the hemispherical lens 8 are pressed against the buffer member 7. Further, the wiring board 9 is positioned by the recess 4 and the hemispherical lens 8 is positioned by the buffer member 7 so that the optical axis OA of the hemispherical lens 8 passes just through a photoconductive antenna part of the photoconductive antenna element 17.

Abstract: This invention relates to a photoconductive antenna element having a structure capable of preventing element characteristics from deteriorating and attain a smaller size at the same time. This photoconductive antenna element (17) comprises a pair of electrodes (21) formed on a semiconductor layer (19). Each electrode (21) is constituted by an antenna part (22), pad parts (23), and a line part (24) connecting them, while the line part (24) includes a parallel portion (24a) extending from the antenna part (22). In the line part (24) of one electrode (21), a portion other than the antenna region (A) is bent opposite to the other electrode (21). In the line part (24) of the other electrode (21), a portion other than the antenna region (A) is bent opposite to the one electrode (21). This structure can prevent the photoconductive antenna element (17) from deteriorating its element characteristics and make it smaller.

Abstract: A semiconductor photocathode 1 includes: a transparent substrate 11; a first electrode 13, formed on the transparent substrate 11 and enabling passage of light that has been transmitted through the transparent substrate 11; a window layer 14, formed on the first electrode 13 and formed of a semiconductor material with a thickness of no less than 10 nm and no more than 200 nm; a light absorbing layer 15, formed on the window layer 14, formed of a semiconductor material that is lattice matched to the window layer 14, is narrower in energy band gap than the window layer 14, and in which photoelectrons are excited in response to the incidence of light; an electron emission layer 16, formed on the light absorbing layer 15, formed of a semiconductor material that is lattice matched to the light absorbing layer 15, and emitting the photoelectrons excited in the light absorbing layer 15 to the exterior from a surface; and a second electrode 18, formed on the electron emission layer.

Abstract: This invention relates to a photoconductive antenna element having a structure capable of preventing element characteristics from deteriorating and attain a smaller size at the same time. This photoconductive antenna element (17) comprises a pair of electrodes (21) formed on a semiconductor layer (19). Each electrode (21) is constituted by an antenna part (22), pad parts (23), and a line part (24) connecting them, while the line part (24) includes a parallel portion (24a) extending from the antenna part (22). In the line part (24) of one electrode (21), a portion other than the antenna region (A) is bent opposite to the other electrode (21). In the line part (24) of the other electrode (21), a portion other than the antenna region (A) is bent opposite to the one electrode (21). This structure can prevent the photoconductive antenna element (17) from deteriorating its element characteristics and make it smaller.

Abstract: There is disclosed a waveguide structure that propagates surface plasmon waves, comprising: a quantum well structure, disposed on a semiconductor substrate; wherein the quantum well structure has a quantum well layer, in turn having an intersecting region that intersects a hypothetical plane substantially orthogonal to an alignment direction of the quantum well structure with respect to the semiconductor substrate, and a real part of a dielectric constant of the quantum well structure is negative for THz waves of a predetermined wavelength.

Abstract: In a terahertz antenna module 1, a photoconductive antenna element 17 is fixed to a wiring board 9, and electrically connected to an electric signal input/output pin 24 of an electric signal input/output port 23 via a signal electrode of the wiring board 9. Further, a buffer member 7, a hemispherical lens 8, a photoconductive antenna element 17, and the wiring board 9 are disposed in a recess 3 of a container 2 in this order from an opening 6 side of the container 2, and by attaching a cover 25 to the container 2, the wiring board 9, the photoconductive antenna element 17, and the hemispherical lens 8 are pressed against the buffer member 7. Further, the wiring board 9 is positioned by the recess 4 and the hemispherical lens 8 is positioned by the buffer member 7 so that the optical axis OA of the hemispherical lens 8 passes just through a photoconductive antenna part of the photoconductive antenna element 17.

Abstract: A semiconductor device has first and second III-V compound semiconductor layers one of which functions as a photosensitive layer or as a light emitting layer, which are doped with a p-type impurity in a low concentration, and which are joined to each other to make a heterojunction. An energy gap of the second III-V compound semiconductor layer is smaller than that of the first III-V compound semiconductor layer and the p-type dopant in each semiconductor layer is Be or C. At this time, the second III-V compound semiconductor layer may be deposited on the first III-V compound semiconductor layer. The first III-V compound semiconductor layer and the second III-V compound semiconductor layer may contain at least one from each group of (In, Ga, Al) and (As, P, N).

Abstract: A semiconductor photocathode has first and second III-V compound semiconductor layers doped with a p-type impurity and joined to each other to make a heterojunction. The second III-V compound semiconductor layer functions as a light absorbing layer, an energy gap of the second III-V compound semiconductor layer is smaller than that of the first III-V compound semiconductor layer, and Be or C is used as the p-type dopant in each semiconductor layer. At this time, the second III-V compound semiconductor layer may be deposited on the first III-V compound semiconductor layer. The first III-V compound semiconductor layer and the second III-V compound semiconductor layer may contain at least one from each group of (In, Ga, Al) and (As, P, N).

Abstract: There is disclosed a waveguide structure that propagates surface plasmon waves, comprising: a quantum well structure, disposed on a semiconductor substrate; wherein the quantum well structure has a quantum well layer, in turn having an intersecting region that intersects a hypothetical plane substantially orthogonal to an alignment direction of the quantum well structure with respect to the semiconductor substrate, and a real part of a dielectric constant of the quantum well structure is negative for THz waves of a predetermined wavelength.