A device for producing electrical current. In one embodiment, the device comprises a stack of epitaxial layers (from a bottom surface): a p-doped semiconductor reflector layer, a p-doped semiconductor emitter layer, an n-doped semiconductor base layer, and an n-doped semiconductor window layer. A radioisotope source, disposed above or in contact with an uppermost layer of the stack, produces radioisotope decay particles or gamma rays that impinge the stack. The electrical current is produced between the first and second conductive regions by action of the radioisotope decay particles or the gamma rays on the emitter and base layers.

A method of making a single-photon detector includes growing an epitaxial multi-layer structure that includes a buffer layer, an absorption layer, a transition layer, a field control charge layer, a multiplication layer, an inversion layer, a migration layer, a window layer, and an Ohmic contact layer sequentially on a substrate. A curved diffusion region is formed in the window layer and the Ohmic contact layer via a diffusion process. A mesa structure is formed by etching the epitaxial multi-layer. A light input window is formed on the substrate. A p-type electrode is formed on the Ohmic contact layer, and an n-type electrode is formed on the substrate. The inversion layer provides supplementary regulation of an electric field distribution that is regulated by the field control charge layer. A single-photon detector made from the method, and a single-photon detector array made with a multitude of the single-photon detectors are also provided.

An integrated microwave photonics (IMWP) apparatus is provided using sapphire as a platform. The IMWP apparatus includes: a sapphire substrate having a step-terrace surface; and a III-V stack layer epitaxially grown on the sapphire substrate. The III-V stack layer includes: a first III-V layer disposed on the sapphire substrate; a low temperature (LT) III-V buffer layer disposed on the first III-V layer; multiple second III-V layers disposed and stacked on the LT III-V buffer layer; a third III-V layer disposed on the second III-V layers; a III-V quantum well layer disposed on the third III-V layers; and a fourth III-V layer disposed on the III-V quantum well layer. The second III-V layers are respectively annealed. A growth temperature of the LT III-V layer and a growth temperature of the III-V quantum well layer are lower than a growth temperature of each of the first, second, third and fourth III-V layers.

Systems, devices, and methods for optical sensing applications. An example multi-wavelength light emitter structure including a substrate; and a vertical structure over the substrate and extending vertically away from the substrate along an axis, the vertical structure comprising a first active region including one or more cascade stages of superlattices for light emission at a first wavelength; a second active region including one or more cascade stages of superlattices for light emission at a second wavelength different from the first wavelength, wherein the second active region is closer to the substrate than the first active region and spaced apart from the first active region; and an electrically conductive material along sidewalls of at least one of the first active region or the second active region.

A photoconductive transducer intended to generate or detect waves in the terahertz frequency domain or in the picosecond pulse domain is provided. The transducer comprises a three-dimensional structure that includes, in this order, a first planar electrode, an array of nano-columns embedded in a layer of resist and a second planar electrode parallel to the first planar electrode. The design of the transducer increases the optical-to-terahertz conversion efficiency by means of photonic and plasmonic resonances and by means of high and homogeneous electric fields. The height of the nano-columns as well as the thickness of the resist range between 100 nanometres and 400 nanometres. The width of the nano-columns is between 100 nanometres and 400 nanometres, the distance between two adjacent nano-columns is between 300 nanometres and 500 nanometres, the nano-columns are made of a III-V semiconductor. The second electrode is transparent, so as to allow the transmission of a laser source towards the photo-absorbing nano-columns.

A photoconductive transducer intended to generate or detect waves in the terahertz frequency domain or in the picosecond pulse domain is provided. The transducer comprises a three-dimensional structure that includes, in this order, a first planar electrode, an array of nano-columns embedded in a layer of resist and a second planar electrode parallel to the first planar electrode. The design of the transducer increases the optical-to-terahertz conversion efficiency by means of photonic and plasmonic resonances and by means of high and homogeneous electric fields. The height of the nano-columns as well as the thickness of the resist range between 100 nanometres and 400 nanometres. The width of the nano-columns is between 100 nanometres and 400 nanometres, the distance between two adjacent nano-columns is between 300 nanometres and 500 nanometres, the nano-columns are made of a III-V semiconductor. The second electrode is transparent, so as to allow the transmission of a laser source towards the photo-absorbing nano-columns.

A PIN diode detector includes a substrate. The PIN diode detector further includes a plurality of PIN diode wells in a pixel region, wherein each of the plurality of PIN diode wells has a first dopant type. The PIN diode detector further includes a connecting ring well and a plurality of floating ring wells in a peripheral region, wherein the connecting ring well and plurality of floating ring wells have the first dopant type. The PIN diode detector further includes a field stop ring well surrounding the plurality of floating ring wells, wherein the field stop ring well has a second dopant type opposite the first dopant type. The PIN diode detector further includes a blanket doped region. The blanket doped region extends continuously through an entirety of the pixel region and an entirety of the peripheral region, and the blanket doped region has the second dopant type.

An infrared detector and a method for forming it are provided. The detector includes absorber, barrier, and contact regions. The absorber region includes a first semiconductor material, with a first lattice constant, that produces charge carriers in response to infrared light. The barrier region is disposed on the absorber region and comprises a superlatice that includes (i) first barrier region layers comprising the first semiconductor material, and (ii) second barrier region layers comprising a second semiconductor material, different from, but lattice matched to, the first semiconductor material. The first and second barrier region layers are alternatingly arranged. The contact region is disposed on the barrier region and comprises a superlattice that includes (i) first contact region layers comprising the first semiconductor material, and (ii) second contact region layers comprising the second semiconductor material layer. The first and second contact region layers are alternatingly arranged.

An electromagnetic radiation detector includes an InP substrate having a first surface opposite a second surface; a first InGaAs electromagnetic radiation absorber stacked on the first surface and configured to absorb a first set of electromagnetic radiation wavelengths; a set of one or more buffer layers stacked on the first InGaAs electromagnetic radiation absorber and configured to absorb at least some of the first set of electromagnetic radiation wavelengths; a second InGaAs electromagnetic radiation absorber stacked on the set of one or more buffer layers and configured to absorb a second set of electromagnetic radiation wavelengths; and an immersion condenser lens formed on the second surface and configured to direct electromagnetic radiation through the InP substrate and toward the first InGaAs electromagnetic radiation absorber and the second InGaAs electromagnetic radiation absorber.

A method of fabricating multijunction solar cell including an upper solar subcell and having an emitter of p conductivity type with a first band gap, and a base of n conductivity type with a second band gap greater than the first band gap; a lower solar subcell disposed below the upper solar subcell having an emitter of p conductivity type with a third band gap, and a base of n conductivity type with a fourth band gap greater than the third band gap; and an intermediate grading interlayer disposed between the upper and lower solar subcells and having a graded lattice constant that matches the upper first subcell on a first side and the second solar subcell on the second side opposite the first side, and having a fifth band gap that is greater than the second band gap of the upper solar subcell.