Photovoltaic devices including direct gap III-V absorber materials and operatively associated back structures enhance efficiency by enabling photon recycling. The back structures of the photovoltaic devices include wide bandgap III-V layers, highly doped (In)GaAs layers, patterned oxide layers and metal reflectors that directly contact the highly doped (In)GaAs layers through vias formed in the back structures. Localized ohmic contacts are formed in the back structures of the devices.

A superlattice and method for forming that superlattice are disclosed. In particular, an engineered layered single crystal structure forming a superlattice is disclosed. The superlattice provides p-type or n-type conductivity, and comprises alternating host layers and impurity layers, wherein: the host layers consist essentially of a semiconductor material; and the impurity layers consist of a donor or acceptor material.

The present disclosure provides an avalanche photodetector and a preparation method therefor. The avalanche photodetector comprises: a substrate, the surface of which comprises a first semiconductor layer; and a second semiconductor layer located on the substrate, wherein the first semiconductor layer comprises a first P-type doped region, a second P-type doped region, a third N-type doped region, a first intrinsic region, a third P-type doped region, a second intrinsic region, a second N-type doped region and a first N-type doped region which are sequentially arranged in a first direction, the dopant concentrations of the first to third P-type doped regions are sequentially decreased, the dopant concentrations of the first to third N-type doped regions are sequentially decreased, and the first direction is an electron flow direction; the second semiconductor layer sequentially covers part of the second P-type doped region, the third N-type doped region, the first intrinsic region and the third P-type doped region in the first direction; the first N-type doped region is connected to a first electrode; the third P-type doped region is connected to a second electrode; and the first N-type doped region is connected to a third electrode.

The present disclosure generally relates to a solar cell device that a first Bragg reflector disposed below a first solar cell and a second Bragg reflector disposed below the first Bragg reflector, wherein the first solar cell comprises a dilute nitride composition and has a first bandgap, wherein the first Bragg reflector is operable to reflect a first range of radiation wavelengths back into the first solar cell and the second Bragg reflector is operable to reflect a third range of wavelengths back into the first solar cell, and the first Bragg reflector and the second Bragg reflector are operable to cool the solar cell device by reflecting a second range of radiation wavelengths that are outside the photogeneration wavelength range of the first solar cell or that are weakly absorbed by the first solar cell.

The present disclosure generally relates to a solar cell device that includes a substrate comprising a front side surface and a backside surface; an epitaxial region overlying the substrate, wherein the epitaxial region comprises a first Bragg reflector disposed below a first solar cell, wherein the first solar cell has a first bandgap, wherein the first Bragg reflector is operable to reflect a first range of radiation wavelengths back into the first solar cell, and is operable to cool the solar cell device by reflecting a second range of radiation wavelengths that are outside the photogeneration wavelength range of the first solar cell or that are weakly absorbed by the first solar cell, and may additionally comprise a second Bragg reflector operable to reflect a third range of radiation wavelengths back into the first solar cell.

A multi-junction solar cell having at least three partial cells having an emitter and a base. The first partial cell comprises a first layer of a compound containing at least the elements GaInP, and the energy band gap of the first layer is greater than 1.75 eV, and wherein the second partial cell has a second layer of a compound having at least the elements GaAs and the lattice constant of the second layer is in the range between 5.635 and 5.675 , and wherein the third partial cell has a third layer of a compound having at least the elements GaInAs and the energy band gap of the third layer is smaller than 1.25 eV and the lattice constant of the third layer is greater than 5.700 .

An nitride semiconductor device for the improvement of lower operational voltage or increased emitting output, comprises an active layer comprising quantum well layer or layers and barrier layer or layers between n-type nitride. semiconductor layers and p-type nitride semiconductor layers, wherein said quantum layer in said active layer comprises InxGa1xN (0<x<1) having a peak wavelength of 450 to 540 nm and said active layer comprises laminating layers of 9 to 13, in which at most 3 layers from the side of said n-type nitride semiconductor layers are doped with an n-type impurity selected from the group consisting of Si, Ge and Sn in a range of 510.sup.16 to 210.sup.18/cm.sup.3.

A superlattice and method for forming that superlattice are disclosed. In particular, an engineered layered single crystal structure forming a superlattice is disclosed. The superlattice provides p-type or n-type conductivity, and comprises alternating host layers and impurity layers, wherein: the host layers consist essentially of a semiconductor material; and the impurity layers consist essentially of a corresponding donor or acceptor material.

A photodiode includes a light absorbing layer including a first superlattice structure that includes first semiconductor layers and second semiconductor layers, the first superlattice structure having a band structure sensitive to infrared light; a p-type semiconductor region; and an intermediate layer disposed between the p-type semiconductor region and the light absorbing layer, the intermediate layer having a conduction band having a bottom energy level lower than that of the p-type semiconductor region.

Photovoltaic devices including direct gap III-V absorber materials and operatively associated back structures enhance efficiency by enabling photon recycling. The back structures of the photovoltaic devices include wide bandgap III-V layers, highly doped (In)GaAs layers, patterned oxide layers and metal reflectors that directly contact the highly doped (In)GaAs layers through vias formed in the back structures. Localized ohmic contacts are formed in the back structures of the devices.