Abstract: Disclosed is a semiconductor-liquid junction based photoelectrochemical (PEC) cell for the unassisted solar splitting of water into hydrogen and oxygen gas, the solar-driven reduction of CO2 to higher-order hydrocarbons, and the solar-driven synthesis of NH3. The disclosed system can employ a photocathode based upon wurtzite hexagonal semiconductors that can be tailored with proper band alignment for the redox potentials for water, CO2 reduction, and NH3 production, and with bandgap energy for maximum solar absorption. The design maximizes the carrier collection efficiency by leveraging spontaneous and piezoelectric polarization in these materials systems to generate hot electrons within the photocathode. These electrons have sufficient excess energy, preserved at a designed energy capture region, to overcome the kinetic overpotential (surface chemistry limitation) required for the reactions to occur at a high rate.

Abstract: Disclosed is a semiconductor-liquid junction based photoelectrochemical (PEC) cell for the unassisted solar splitting of water into hydrogen and oxygen gas, the solar-driven reduction of CO2 to higher-order hydrocarbons, and the solar-driven synthesis of NH3. The disclosed system can employ a photocathode based upon wurtzite hexagonal semiconductors that can be tailored with proper band alignment for the redox potentials for water, CO2 reduction, and NH3 production, and with bandgap energy for maximum solar absorption. The design maximizes the carrier collection efficiency by leveraging spontaneous and piezoelectric polarization in these materials systems to generate hot electrons within the photocathode. These electrons have sufficient excess energy, preserved at a designed energy capture region, to overcome the kinetic overpotential (surface chemistry limitation) required for the reactions to occur at a high rate.

Abstract: A photodiode for detecting photons comprising a substrate; first semiconducting region suitable for forming a contact thereon; a first contact; a second semiconducting region comprising an absorption region for the photons and being formed of a semiconductor having one or more of a high surface recombination velocity or a high interface recombination velocity; a second contact operatively associated with the second region; the first semiconducting region and the second semiconducting region forming a first interface; the second semiconducting region being configured such that reverse biasing the photodiode between the first and second contacts results in the absorption region having a portion depleted of electrical carriers and an undepleted portion at the reverse bias point of operation; the undepleted portion being smaller than the absorption depth for photons; whereby the depletion results in the creation of an electric field and photogenerated carriers are collected by drift; and a method of making.

Abstract: A reflection-mode waveplate for operation in the terahertz region by shifting the phase between two perpendicular polarization components of the light wave, comprising a ground plane; an array of polygonal unit cells; the polygonal unit cells comprising a polymer positioned between the ground plane and the exterior of the array of polygonal patches.

Abstract: A photodiode comprising a substrate; first semiconducting region; first contact; second region comprising an absorption region for the photons having a predetermined energy range; the second region being formed of a semiconductor having a high surface or interface recombination velocity; a third semiconducting region transparent at the predetermined photon energy range suitable for making an operative connection to a second contact; the second and third regions forming a second interface; the first and second regions forming a first interface; the second region being configured such that biasing the photodiode results in depletion of the second region from the first interface to the second interface or at least one of the absorption depth and the sum of the absorption depth and diffusion length from the second interface; the depletion resulting in the creation of an electric field whereby photogenerated carriers are collected by drift and a method of making the foregoing.

Abstract: A photodiode for detecting photons comprising a substrate; first semiconducting region suitable for forming a contact thereon; a first contact; a second semiconducting region comprising an absorption region for the photons and being formed of a semiconductor having one or more of a high surface recombination velocity or a high interface recombination velocity; a second contact operatively associated with the second region; the first semiconducting region and the second semiconducting region forming a first interface; the second semiconducting region being configured such that reverse biasing the photodiode between the first and second contacts results in the absorption region having a portion depleted of electrical carriers and an undepleted portion at the reverse bias point of operation; the undepleted portion being smaller than the absorption depth for photons; whereby the depletion results in the creation of an electric field and photogenerated carriers are collected by drift; and a method of making.

Abstract: A method of making and a photodetector comprising a substrate; a p-type or n-type layer; first and second region each having polarizations, a first interface therebetween, the magnitudes and directions of the first and second polarizations being such that a scalar projection of second polarization on the growth direction relative to the scalar projection of the first polarization projected onto the growth direction is sufficient to create a first interface charge; and a third region suitable for forming one of an n-metal or p-metal contact thereon having a third polarization, a second interface between the second and third regions, the third polarization having a scalar projection on the growth direction that, relative to scalar projection of the second polarization onto the growth direction, is sufficient to create a second interface charge; the first and second interface charges creating an electrostatic potential barrier to carriers defining a predetermined wavelength range.

Abstract: A method of making and a photodetector comprising a substrate; a p-type or n-type layer; first and second region each having polarizations, a first interface therebetween, the magnitudes and directions of the first and second polarizations being such that a scalar projection of second polarization on the growth direction relative to the scalar projection of the first polarization projected onto the growth direction is sufficient to create a first interface charge; and a third region suitable for forming one of an n-metal or p-metal contact thereon having a third polarization, a second interface between the second and third regions, the third polarization having a scalar projection on the growth direction that, relative to scalar projection of the second polarization onto the growth direction, is sufficient to create a second interface charge; the first and second interface charges creating an electrostatic potential barrier to carriers defining a predetermined wavelength range.

Abstract: A reflection-mode waveplate for operation in the terahertz region by shifting the phase between two perpendicular polarization components of the light wave, comprising a ground plane; an array of polygonal unit cells; the polygonal unit cells comprising a polymer positioned between the ground plane and the exterior of the array of polygonal patches.

Abstract: An AlGaN composition is provided comprising a group III-Nitride active region layer, for use in an active region of a UV light emitting device, wherein light-generation occurs through radiative recombination of carriers in nanometer scale size, compositionally inhomogeneous regions having band-gap energy less than the surrounding material. Further, a semiconductor UV light emitting device having an active region layer comprised of the AlGaN composition above is provided, as well as a method of producing the AlGaN composition and semiconductor UV light emitting device, involving molecular beam epitaxy.

Abstract: A method and device for generating terahertz radiation comprising a substrate; a plurality of segments of polar crystal material formed on the substrate, the segments having an internal electric polarization; each segment comprising at least two edges oriented substantially perpendicular to the polar axis such that the electric polarization terminates at the edges and the segment comprises a majority of positive charges on one edge and a majority of negative charges on the opposite edge thereby leading to creation of an internal electric field; whereby when irradiated by a pulsed source of duration less than one picosecond, electron-hole pairs are generated within the segments and the internal electric field separates and accelerates the electron-hole pairs to thereby produce terahertz radiation.

Abstract: A detection device comprising a photodetector comprising a first semiconductor layer through which light first enters the photodetector; the first semiconductor layer formed of a first semiconductor material crystal lattice which terminates at an interface creating a first interface charge; the first semiconductor layer being an absorption layer in which photons in a predetermined wavelength range are absorbed and create photogenerated carriers; and a second polar semiconductor layer deposited on the crystal lattice of the first semiconductor layer substantially transparent to light in the predetermined wavelength range and having a total polarization different from the first semiconductor layer so that a second interface charge is induced at the interface between the first and second semiconductor layers; the induced second interface charge reduces or substantially cancels the first interface charge so as to increase the collection of photogenerated carriers by the photodetector.

Abstract: An avalanche photodetector comprising a multiplication layer formed of a first material having a first polarization; the multiplication layer having a first electric field upon application of a bias voltage; an absorption layer formed of a second material having a second polarization forming an interface with the multiplication layer; the absorption layer having a second electric field upon application of the bias voltage, the second electric field being less than the first electric field or substantially zero, carriers created by light absorbed in the absorption layer being multiplied in the multiplication layer due to the first electric field; the absorption layer having a second polarization which is greater or less than the first polarization to thereby create an interface charge; the interface charge being positive when the first material predominately multiplies holes, the interface charge being negative when the first material predominately multiplies electrons, the change in electric field at the inte

Abstract: A method and device for generating terahertz radiation comprising a plurality of layers of polar crystal material operative to emit terahertz radiation; the plurality of layers comprising transport layers and divider layers, the plane of the layers being not parallel to the polar axis, the interface between the transport layers and divider layers forming boundaries at which the internal electric polarization terminates leading to charges accumulating at the boundaries, and creation of internal electric fields oriented along the polar axis.

Abstract: An avalanche photodetector comprising a multiplication layer formed of a first material having a first polarization; the multiplication layer having a first electric field upon application of a bias voltage; an absorption layer formed of a second material having a second polarization forming an interface with the multiplication layer; the absorption layer having a second electric field upon application of the bias voltage, the second electric field being less than the first electric field or substantially zero, carriers created by light absorbed in the absorption layer being multiplied in the multiplication layer due to the first electric field; the absorption layer having a second polarization which is greater or less than the first polarization to thereby create an interface charge; the interface charge being positive when the first material predominately multiplies holes, the interface charge being negative when the first material predominately multiplies electrons, the change in electric field at the inte

Abstract: A detection device comprising a photodetector comprising a first semiconductor layer through which light first enters the photodetector; the first semiconductor layer to semiconductor material crystal lattice which terminates at an interface; the discontinuity of the semiconductor crystal lattice at the interface creating a first interface charge; the first semiconductor layer being an absorption layer in which photons in a predetermined wavelength range are absorbed and create photogenerated carriers; and a second polar semiconductor layer deposited on the crystal lattice of the first semiconductor layer, the second polar semiconductor being substantially transparent to light in the predetermined wavelength range, the second polar semiconductor layer having a total polarization different from the first semiconductor layer so that a second interface charge is induced at the interface between the first and second semiconductor layers; the induced second interface charge reduces or substantially cancels the fir

Abstract: A method and device for generating terahertz radiation comprising a substrate; a plurality of segments of polar crystal material formed on the substrate, the segments having an internal electric polarization; each segment comprising at least two edges oriented substantially perpendicular to the polar axis such that the electric polarization terminates at the edges and the segment comprises a majority of positive charges on one edge and a majority of negative charges on the opposite edge thereby leading to creation of an internal electric field; whereby when irradiated by a pulsed source of duration less than one picosecond, electron-hole pairs are generated within the segments and the internal electric field separates and accelerates the electron-hole pairs to thereby produce terahertz radiation.

Abstract: A method and device for generating terahertz radiation comprising a plurality of layers of polar crystal material operative to emit terahertz radiation; the plurality of layers comprising transport layers and divider layers, the plane of the layers being not parallel to the polar axis, the interface between the transport layers and divider layers forming boundaries at which the internal electric polarization terminates leading to charges accumulating at the boundaries, and creation of internal electric fields oriented along the polar axis; whereby when irradiated by a pulsed source of duration less than one picosecond, a time-varying and spatially nonuniform distribution of carriers is created in the growth direction of the polar crystal material thereby generating a first time-varying current due to diffusion of the carriers; the internal electric fields accelerating the carriers generated by the pulsed radiation source operating to produce a second time-varying current that is additive with the first time-v

Abstract: A light emitting device comprising: a polar template; a p-type layer grown thereon; the p-type layer having a first polarization vector having a first projection relative to a growth direction; an n-type layer grown on the p-type layer; the n-type layer having a second polarization vector that is larger than the first polarization vector; the n-type layer and p-type layer forming an interface. Another preferred embodiment light emitting device comprises a polar template; an n-type layer grown on the template; the n-type layer having a first polarization vector having a first projection relative to a growth direction; a p-type layer grown on the n-type layer having a second polarization vector that is larger than the first polarization vector. In both embodiments, the first polarization vector in the p-layer and second polarization vector in the n-layer create discontinuity at the interface resulting in a negative charge appearing at the interface.

Abstract: A method and device for generating terahertz radiation comprising a polar crystal material layer operative to emit terahertz radiation; the polar crystal material layer comprising a plurality of stacking faults; the stacking faults lying substantially perpendicular to the polar axis and forming boundaries at which the internal electric polarization terminates leading to charges accumulating at the boundaries, and creation of internal electric fields oriented along the polar axis; a pulsed radiation source for creating photogenerated carriers in the polar crystal material; whereby the photogenerated carriers accelerate in the internal electric fields associated with the termination of the internal electric polarization by the stacking faults to thereby generate terahertz radiation.