Abstract: A device includes a substrate and a heterostructure supported by the substrate. The heterostructure includes a set of quantum dot structures, each quantum dot structure of the set of quantum dot structures including a semiconductor material, and a layered material disposed between the set of quantum dot structures and the substrate. The layered material includes a plurality of monolayers such that adjacent monolayers of the plurality of monolayers are bonded to one another via van der Waals forces, and the semiconductor material of each quantum dot structure of the set of quantum dot structures exhibits bonding via van der Waals forces.

Abstract: An all-epitaxial, electrically injected surface-emitting green laser operates in a range of about 520-560 nanometers (nm). At 523 nm, for example, the device exhibits a threshold current density of approximately 0.4 kilo-amperes per square centimeter (kA/cm2), which is over one order of magnitude lower than that of previously reported blue laser diodes.

Abstract: A method for fabricating a light emitting diode (LED) device includes forming a nitrogen-polar (N-polar) template on a substrate, growing a first N-polar, III-nitride semiconductor segment of a nanostructure, growing a N-polar active region of the nanostructure, the N-polar active region being supported by the first N-polar, III-nitride semiconductor segment, the N-polar active region including a ternary or quaternary III-nitride semiconductor material, and growing a second N-polar, III-nitride semiconductor segment of the nanostructure, the second N-polar segment being supported by the N-polar active region.

Abstract: A method includes of fabricating a heterostructure includes growing epitaxially, in a growth chamber, a first semiconductor layer of the heterostructure, the first semiconductor layer comprising a III-nitride semiconductor material, the first semiconductor layer being supported by a substrate, and, after growing the first semiconductor layer, growing epitaxially, in the growth chamber, a second semiconductor layer of the heterostructure such that the second semiconductor layer is supported by the first semiconductor layer, the second semiconductor layer comprising a quaternary or higher order III-nitride alloy.

Abstract: The presented devices and methods are directed to efficient and effective photon emission. In one embodiment, high-performance tunnel junction deep ultraviolet (UV) light-emitting diodes (LEDs) are created using plasma-assisted molecular beam epitaxy. The device heterostructure was grown under slightly Ga-rich conditions to promote the formation of nanoscale clusters in the active region. The nanoscale clusters can act as charge containment configurations. In one exemplary implementation, a device operates at approximately 255 nm light emission with a maximum external quantum efficiency (EPE) of 7.2% and wall-plug efficiency (WPE) of 4%, which are nearly one to two orders of magnitude higher than previously reported tunnel junction devices operating at this wavelength.

Abstract: In accordance with aspects of the present technology, a unique charge carrier transfer process from c-plane InGaN to semipolar-plane InGaN formed spontaneously in nanowire heterostructures can effectively reduce the instantaneous charge carrier density in the active region, thereby leading to significantly enhanced emission efficiency in the deep red wavelength. Furthermore, the total built-in electric field can be reduced to a few kV/cm by cancelling the piezoelectric polarization with spontaneous polarization in strain-relaxed high indium composition InGaN/GaN heterostructures. An ultra-stable red emission color can be achieved in InGaN over four orders of magnitude of excitation power range. Accordingly, aspects of the present technology advantageously provide a method for addressing some of the fundamental issues in light-emitting devices and advantageously enables the design of high efficiency and high stability optoelectronic devices.

Abstract: A device includes a substrate and a semiconductor heterostructure supported by the substrate. The semiconductor heterostructure includes a first semiconductor layer supported by the substrate and including a first III-nitride semiconductor material, and a second semiconductor layer supported by the first semiconductor layer and including a second III-nitride semiconductor material. The second III-nitride semiconductor material includes scandium. The first and second semiconductor layers are nitrogen-polar.

Abstract: A method of promoting a chemical reaction includes immersing a device in a solution contained in a reaction chamber, the device including a substrate and a plurality of conductive projections supported by the substrate, each conductive projection of the plurality of conductive projections having a semiconductor composition, irradiating the device to drive the chemical reaction, and controlling a temperature of the solution contained in the reaction chamber such that the temperature is maintained in a temperature range closer to a boiling temperature of the solution than a freezing temperature of the solution

Abstract: A device for catalytic conversion of carbon dioxide (CO2) includes a substrate having a surface, an array of conductive projections supported by the substrate and extending outward from the surface of the substrate, each conductive projection of the array of conductive projections having a semiconductor composition, and a plurality of nanoparticles disposed over the array of conductive projections, each nanoparticle of the plurality of nanoparticles being configured for the catalytic conversion of carbon dioxide (CO2). Each nanoparticle of the plurality of nanoparticles includes a Group VA element, the Group VA element being a metal or a metalloid.

Abstract: Various embodiments are based on the study of the design, epitaxy, and performance characteristics of deep ultraviolet (UV) AlGaN light emitting diodes (LEDs). By combining tunnel junction and polarization-engineered AlGaN electron blocking layer, a maximum external quantum efficiency and wall-plug efficiency of 0.35% and 0.21%, respectively, were measured for devices operating at approximately 245 nanometers (nm), which are over one order of magnitude higher than previously reported tunnel junction devices at this wavelength. Severe efficiency droop, however, was measured at very low current densities (approximately 0.25 A/cm2), which, together with the transverse magnetic (TM) polarized emission, are identified to be the primary limiting factors for the device performance. Detailed electrical and optical analysis further show that the observed efficiency droop is largely due to an electrical effect, instead of an optical phenomenon.

Abstract: A method of fabricating a heterostructure includes providing a substrate, and implementing a non-sputtered, epitaxial growth procedure at a growth temperature to form a wurtzite structure supported by the substrate. The wurtzite structure includes an alloy of a III-nitride material. The non-sputtered, epitaxial growth procedure is configured to incorporate a group IIIB element into the alloy of the III-nitride material. The growth temperature is at a level such that the wurtzite structure exhibits a breakdown field strength greater than a ferroelectric coercive field strength of the wurtzite structure.

Abstract: Monolithic integration of multicolor light-emitting diodes with highly spatially uniform emission wavelength are realized in a single selective area epitaxy process. Pronounced emission peaks with very narrow spectral linewidths are also achieved. The indium contents and emission colors are tuned by precisely controlling the nanowire emitter diameter and lattice constant. The emission wavelengths exhibit small variations of only a few nanometers among individual nanowire emitters over an areal region.

Abstract: An electrode of a chemical cell includes a substrate having a surface, an array of conductive projections supported by the substrate and extending outward from the surface of the substrate, each conductive projection of the array of conductive projections having a semiconductor composition for reduction of carbon dioxide (CO2) in the chemical cell, and a catalyst arrangement disposed along each conductive projection of the array of conductive projections, the catalyst arrangement including a copper-based catalyst and an iron-based catalyst for the reduction of carbon dioxide (CO2) in the chemical cell.

Abstract: A method of fabricating a device includes providing a substrate of the device, forming a structure of the device, the structure being supported by the substrate, having a semiconductor composition, and including a surface, where nitrogen is present at the surface, and incorporating oxygen into the surface to form a stabilizing layer on the surface.

Abstract: An epitaxial growth process, referred to as metal-semiconductor junction assisted epitaxy, of ultrawide bandgap aluminum gallium nitride (AlGaN) is disclosed. The epitaxy of AlGaN is performed in metal-rich (e.g., Ga-rich) conditions using plasma-assisted molecular beam epitaxy. The excess Ga layer leads to the formation of a metal-semiconductor junction during the epitaxy of magnesium (Mg)-doped AlGaN, which pins the Fermi level away from the valence band at the growth front. The Fermi level position is decoupled from Mg-dopant incorporation; that is, the surface band bending allows the formation of a nearly n-type growth front despite p-type dopant incorporation. With controlled tuning of the Fermi level by an in-situ metal-semiconductor junction during epitaxy, efficient p-type conduction can be achieved for large bandgap AlGaN.

Abstract: An all-epitaxial, electrically injected surface-emitting green laser operates in a range of about 520-560 nanometers (nm). At 523 nm, for example, the device exhibits a threshold current density of approximately 0.4 kilo-amperes per square centimeter (kA/cm2), which is over one order of magnitude lower than that of previously reported blue laser diodes.

Abstract: An epitaxial growth process, referred to as metal-semiconductor junction assisted epitaxy, of ultrawide bandgap aluminum gallium nitride (AlGaN) is disclosed. The epitaxy of AlGaN is performed in metal-rich (e.g., Ga-rich) conditions using plasma-assisted molecular beam epitaxy. The excess Ga layer leads to the formation of a metal-semiconductor junction during the epitaxy of magnesium (Mg)-doped AlGaN, which pins the Fermi level away from the valence band at the growth front. The Fermi level position is decoupled from Mg-dopant incorporation; that is, the surface band bending allows the formation of a nearly n-type growth front despite p-type dopant incorporation. With controlled tuning of the Fermi level by an in-situ metal-semiconductor junction during epitaxy, efficient p-type conduction can be achieved for large bandgap AlGaN.

Abstract: A device includes a substrate having a surface, an array of conductive projections supported by the substrate and extending outward from the surface of the substrate, a plurality of catalyst nanoparticles disposed over the array of conductive projections, and an oxide layer covering the plurality of catalyst nanoparticles and the array of conductive projections. The oxide layer has a thickness on the order of a size of each catalyst nanoparticle of the plurality of catalyst nanoparticles.

Abstract: A nanowire can include a first semiconductor portion, a second portion including a quantum structure disposed on the first portion, and a second semiconductor portion disposed on the second portion opposite the first portion. The quantum structure can include one or more quantum core structures and a quantum core shell disposed about the one or more quantum core structures. The one or more quantum core structures can include one or more quantum disks, quantum arch-shaped forms, quantum wells, quantum dots within quantum wells or combinations thereof.

Abstract: GaN-based nanowire heterostructures have been intensively studied for applications in light emitting diodes (LEDs), lasers, solar cells and solar fuel devices. Surface charge properties play a dominant role on the device performance and have been addressed within the prior art by use of a relatively thick large bandgap AlGaN shell covering the surfaces of axial InGaN nanowire LED heterostructures has been explored and shown substantial promise in reducing surface recombination leading to improved carrier injection efficiency and output power. However, these lead to increased complexity in device design, growth and fabrication processes thereby reducing yield/performance and increasing costs for devices. Accordingly, there are taught self-organising InGaN/AlGaN core-shell quaternary nanowire heterostructures wherein the In-rich core and Al-rich shell spontaneously form during the growth process.