Terahertz imaging systems for endoscopy are provided. Terahertz imaging systems can be utilized in scanning tissue. Terahertz imaging systems in accordance with embodiments of the invention can include terahertz sources, terahertz detectors, and/or rotating elements. The terahertz sources can generate terahertz radiation and have plasmonic contact electrodes that can be illuminated by optical pump beams. The terahertz detectors can receive terahertz field data. The terahertz source and detector can be arranged in an array. The rotating elements can be mirror mounted at a particular angle on a micromotor. The terahertz source, rotating element, and terahertz detector can be arranged in an catheter.

A photovoltaic cell can include a dopant in contact with a semiconductor layer.

A high-voltage switch is adapted for use as a medium-voltage direct current circuit breaker, which provides a low-cost, small-footprint device to mitigate system faults. In one example, a method for operating a wideband optical device includes illuminating the wide bandgap optical device with a light within a first range of wavelengths and a first average intensity, allowing a current to propagate therethrough without substantial absorption of the current, illuminating the wide bandgap optical device with light within the first range of wavelengths and a second average intensity that is lower than the first average intensity to allow a sustained current flow though the wide bandgap optical device, and illuminating the wide bandgap optical device with light within a second range of wavelengths to stop or substantially restrict propagation of the current through the wide gap material.

Heterostructures containing one or more sheets of positive charge, or alternately stacked AlGaN barriers and AlGaN wells with specified thickness are provided. Also provided are multiple quantum well structures and p-type contacts. The heterostructures, the multiple quantum well structures and the p-type contacts can be used in light emitting devices and photodetectors.

Monolithic, lateral series photovoltaic and photodiode devices on an insulating substrate are provided. In one aspect, a method of forming a photovoltaic device includes: forming a photovoltaic stack on an insulating substrate that includes: a bottom contact layer disposed on the insulating substrate, a BSF layer disposed on the bottom contact layer, a junction layer disposed on the BSF layer, a window layer disposed on the junction layer, and a top contact layer disposed on the window layer; patterning the top contact layer, the window layer, the junction layer, the BSF layer and the bottom contact layer into individual device stacks; forming contact pads on patterned portions of the bottom/top contact layers in each of the device stacks; and forming interconnects in contact with the contact pads that serially connect the device stacks. A photovoltaic device is also provided.

Methods of forming a p-type IV-doped III-VI semiconductor are provided which comprise exposing a substrate to a vapor composition comprising a group III precursor comprising a group III element, a group VI precursor comprising a group VI element, and a group IV precursor comprising a group IV element, under conditions to form a p-type IV-doped III-VI semiconductor via metalorganic chemical vapor deposition (MOCVD) on the substrate. Embodiments make use of a flow ratio defined as a flow rate of the group VI precursor to a flow rate of the group III precursor wherein the flow ratio is below an inversion flow ratio value for the IV-doped III-VI semiconductor.

A solar cell including a nonpolar m-plane GaN substrate, an n-type III-nitride layer, a III-nitride active region, and a p-type III-nitride layer. In one example, the solar cell includes a nonpolar m-plane GaN substrate, a Si-doped GaN layer, a multiplicity of InGaN/GaN layers, and and a Mg-doped GaN layer. A working temperature range of the solar cell is from room temperature to about 500 C., an external quantum efficiency of the solar cell increases by at least a factor of 2 from room temperature to 500 C., and a temperature coefficient of the solar cell is greater than zero up to 350 C.

Heterostructures containing one or more sheets of positive charge, or alternately stacked AlGaN barriers and AlGaN wells with specified thickness are provided. Also provided are multiple quantum well structures and p-type contacts. The heterostructures, the multiple quantum well structures and the p-type contacts can be used in light emitting devices and photodetectors.

Heterostructures containing one or more sheets of positive charge, or alternately stacked AlGaN barriers and AlGaN wells with specified thickness are provided. Also provided are multiple quantum well structures and p-type contacts. The heterostructures, the multiple quantum well structures and the p-type contacts can be used in light emitting devices and photodetectors.

Heterostructures containing one or more sheets of positive charge, or alternately stacked AlGaN barriers and AlGaN wells with specified thickness are provided. Also provided are multiple quantum well structures and p-type contacts. The heterostructures, the multiple quantum well structures and the p-type contacts can be used in light emitting devices and photodetectors.