US Government As Represented by the Secretary of the Army

Anand Venktesh Sampath

Michael Wraback

Paul H Shen

Charles J Collins

Gregory Alan Garrett

H Paul Shen

Lee Ellen Rodak

Vijay S Parameshwaran

Chad Stephen Gallinat

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 COto higher-order hydrocarbons, and the solar-driven synthesis of NH. 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, COreduction, and NHproduction, 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.

Electron acceleration and capture device for preserving excess kinetic energy to drive electrochemical reduction reactions

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.

Enhanced deep ultraviolet photodetector and method thereof

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.

Variable range photodetector and method thereof

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.

Ultraviolet light emitting AlGaN composition and ultraviolet light emitting device containing same

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 interface occurring abruptly at the atomic level; the interface charge creating electric field discontinuity causing first electric field to attain the breakdown field in the multiplication region and the second electric field to be low or zero in the absorption layer to thereby eliminate the need for a doped charge layer and the associated thickness of the doped charge layer required to transition from the low field to the high field. Also claimed is a method of making.

Polarization enhanced avalanche photodetector and method thereof

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. ; and a methodproviding the above.

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Montgomery Village, MD, United States of America

Anand Venktesh Sampath