A scalable voltage source having a number N of partial voltage sources implemented as semiconductor diodes connected to one another in series, wherein each of the partial voltage sources has a semiconductor diode with a p-n junction. A tunnel diode is formed between sequential pairs of partial voltage sources, wherein the tunnel diode has multiple semiconductor layers with a larger band gap than the band gap of the p/n absorption layers and the semiconductor layers with the larger band gap are each made of a material with modified stoichiometry and/or a different elemental composition than the p/n absorption layers of the semiconductor diode. The partial voltage sources and the tunnel diodes are monolithically integrated together, and jointly form a first stack with a top and a bottom, and the number N of partial voltage sources is greater than or equal to two.

A structure includes a silicon substrate; silicon readout circuitry disposed on a first portion of a top surface of the substrate and a radiation detecting pixel disposed on a second portion of the top surface of the substrate. The pixel has a plurality of radiation detectors connected with the readout circuitry. The plurality of radiation detectors are composed of at least one visible wavelength radiation detector containing germanium and at least one infrared wavelength radiation detector containing a Group III-V semiconductor material. A method includes providing a silicon substrate; forming silicon readout circuitry on a first portion of a top surface of the substrate and forming a radiation detecting pixel, on a second portion of the top surface of the substrate, that has a plurality of radiation detectors formed to contain a visible wavelength detector composed of germanium and an infrared wavelength detector composed of a Group III-V semiconductor material.

A split electrode vertical cavity optical device includes an n-type ohmic contact layer, first through fifth ion implant regions, cathode and anode electrodes, first and second injector terminals, and p and n type modulation doped quantum well structures. The cathode electrode and the first and second ion implant regions are formed on the n-type ohmic contact layer. The third ion implant region is formed on the first ion implant region and contacts the p-type modulation doped QW structure. The fourth ion implant region encompasses the n-type modulation doped QW structure. The first and second injector terminals are formed on the third and fourth ion implant regions, respectively. The fifth ion implant region is formed above the n-type modulation doped QW structure and the anode electrode is formed above the fifth ion implant region.

A semiconductor device includes an n-type ohmic contact layer, cathode and anode electrodes, p-type and n-type modulation doped quantum well (QW) structures, and first and second ion implant regions. The anode electrode is formed on the first ion implant region that contacts the p-type modulation doped QW structure and the cathode electrode is formed by patterning the first and second ion implant regions and the n-type ohmic contact layer. The semiconductor device is configured to operate as at least one of a diode laser and a diode detector. As the diode laser, the semiconductor device emits photons. As the diode detector, the semiconductor device receives an input optical light and generates a photocurrent.

A highly doped layer for interconnecting tunnel junctions in multijunction solar cells is presented. The highly doped layer is a delta doped layer in one or both layers of a tunnel diode junction used to connect two or more p-on-n or n-on-p solar cells in a multijunction solar cell. A delta doped layer is made by interrupting the epitaxial growth of one of the layers of the tunnel diode, depositing a delta dopant at a concentration substantially greater than the concentration used in growing the layer of the tunnel diode, and then continuing to epitaxially grow the remaining tunnel diode.

A photoconductive device that generates or detects terahertz radiation includes a semiconductor layer; a structure portion; and an electrode. The semiconductor layer has a thickness no less than a first propagation distance and no greater than a second propagation distance, the first propagation distance being a distance that the surface plasmon wave propagates through the semiconductor layer in a perpendicular direction of an interface between the semiconductor layer and the structure portion until an electric field intensity of the surface plasmon wave becomes 1/e times the electric field intensity of the surface plasmon wave at the interface, the second propagation distance being a distance that a terahertz wave having an optical phonon absorption frequency of the semiconductor layer propagates through the semiconductor layer in the perpendicular direction until an electric field intensity of the terahertz wave becomes 1/e.sup.2 times the electric field intensity of the terahertz wave at the interface.

A compound photovoltaic cell includes a substrate, a first cell made of a first semiconductor material and formed on the substrate, a tunnel layer, and a second cell made of a second semiconductor material lattice mismatched with a material of the substrate, connected to the first cell via the tunnel layer, and disposed on an incident side with respect to the first cell, wherein band gaps of the first and the second cells become smaller from an incident side to a back side, and wherein the tunnel layer includes a p-type layer disposed on the incident side and a n-type layer disposed on the back side, the p-type layer being a p.sup.+-type (Al)GaInAs layer, the n-type layer being an n.sup.+-type InP layer, an n.sup.+-type GaInP layer having a tensile strain with respect to InP or n.sup.+-type Ga(In)PSb layer having a tensile strain with respect to InP.

Embodiments of the invention generally relate to photovoltaic devices. In one embodiment, a method for forming a gallium arsenide based photovoltaic device includes providing a semiconductor structure, the structure including an absorber layer comprising gallium arsenide. A bypass function is provided in a p-n junction of the semiconductor structure, where under reverse-bias conditions the p-n junction breaks down in a controlled manner by a Zener breakdown effect.

A photoelectric conversion element includes a photoelectric conversion layer having the quantum structure and utilizes intersubband transition in a conduction band. The photoelectric conversion element includes a superlattice semiconductor layer in which a barrier layer and a quantum dot layer as a quantum layer are alternately and repeatedly stacked. The barrier layer includes an indirect transition semiconductor material, and the quantum dot layer has a nano-structure including a direct transition semiconductor material. The indirect transition semiconductor material constituting the barrier layer has a bandgap of more than 1.42 eV at room temperature.

An epitaxial wafer of the present invention includes a substrate composed of a III-V compound semiconductor, a multiple quantum well structure composed of a III-V compound semiconductor and located on the substrate, and a top layer composed of a III-V compound semiconductor and located on the multiple quantum well structure. The substrate has a plane orientation of (100) and an off angle of 0.030 or more and +0.030 or less, and a surface of the top layer has a root-mean-square roughness of less than 10 nm.