An LED system having color tunability in response to variations in driving current density is disclosed. In one example, the system includes a patterned dielectric layer, multiple quantum well (MQW) region, electron blocking layer (EBL), and p-type GaN layer. The EBL is deposited on the MQW region and structured such that the injection of holes into the MQW region is plane-specific. Plane-specific hole injection leads to targeted color emission tied to the level of band bending. The p-type GaN layer is deposited above the EBL and is doped to be a source of holes. For shorter wavelength emission, the p-GaN is designed such that there is adequate hole supply to lower layers of the MQW region. This selective injection of holes in the direction of various crystal planes, together with managed Indium concentration in the MQW region and an adequate supply of holes, enables smooth color tunability.

An LED system having color tunability in response to variations in driving current density is disclosed. In one example, the system includes a patterned dielectric layer, multiple quantum well (MQW) region, electron blocking layer (EBL), and p-type GaN layer. The EBL is deposited on the MQW region and structured such that the injection of holes into the MQW region is plane-specific. Plane-specific hole injection leads to targeted color emission tied to the level of band bending. The p-type GaN layer is deposited above the EBL and is doped to be a source of holes. For shorter wavelength emission, the p-GaN is designed such that there is adequate hole supply to lower layers of the MQW region. This selective injection of holes in the direction of various crystal planes, together with managed Indium concentration in the MQW region and an adequate supply of holes, enables smooth color tunability.

An optoelectronic device including a matrix of axial light-emitting diodes (LEDs). Each LED includes an active layer emitting electromagnetic radiation. The matrix forms a photonic crystal having at least first and second resonant peaks in a plane containing the active layers, each first and second peak amplifying the radiation intensity at a first and second wavelength respectively. Each light emitting diode includes an elongated semiconductor element, having a first portion of a first average diameter, a second portion extending the first portion and having a cross-sectional area decreasing away from the first portion, and the active layer extending the second portion and having a second average diameter strictly less than the first average diameter, the active layers being located at the first peak locations and absent at the secondary peak locations.

An optoelectronic device including a matrix of axial light-emitting diodes (LEDs). Each LED includes an active layer emitting electromagnetic radiation. The matrix forms a photonic crystal having at least first and second resonant peaks in a plane containing the active layers, each first and second peak amplifying the radiation intensity at a first and second wavelength respectively. Each light emitting diode includes an elongated semiconductor element, having a first portion of a first average diameter, a second portion extending the first portion and having a cross-sectional area decreasing away from the first portion, and the active layer extending the second portion and having a second average diameter strictly less than the first average diameter, the active layers being located at the first peak locations and absent at the secondary peak locations.

An inkjet printing apparatus includes: a print head device including an inkjet head to spray a composition for ink including a plurality of bipolar elements; an ink circulation device including an ink storage to store the composition for ink, and transfer the composition for ink to the print head device; an ink injection device to inject the composition for ink into the ink storage; and a temperature adjusting device to adjust a temperature of the composition for ink. The temperature adjusting device includes: a first temperature adjusting device to adjust a temperature to be included in a first reference temperature range; a second temperature adjusting device to adjust a temperature to be included in a second reference temperature range; and a third temperature adjusting device to adjust a temperature to be included in a third reference temperature range.

Nanowire heterostructures are disclosed for high-efficiency light emitting devices, lasers, and related applications. The nanowires may include inversely tapered geometries, core regions configured for quantum confinement of carriers, and radial profiles that provide radial carrier confinement, thereby suppressing non-radiative recombination and enhancing emission efficiency. In some embodiments, the nanowires are grown on silicon substrates using molecular beam epitaxy and emit light in the ultraviolet or visible spectrum. The structures may also enable coherent emission through Anderson localization of light with simplified fabrication.

Nanowire heterostructures are disclosed for high-efficiency light emitting devices, lasers, and related applications. The nanowires may include inversely tapered geometries, core regions configured for quantum confinement of carriers, and radial profiles that provide radial carrier confinement, thereby suppressing non-radiative recombination and enhancing emission efficiency. In some embodiments, the nanowires are grown on silicon substrates using molecular beam epitaxy and emit light in the ultraviolet or visible spectrum. The structures may also enable coherent emission through Anderson localization of light with simplified fabrication.

A light-emitting device of an embodiment of the present disclosure includes: an insulating layer having a first surface and a second surface that are opposed to each other; multiple columnar structures each including a columnar crystalline structure of a first electrically-conductive type erected in a direction perpendicular to the first surface of the insulating layer, and an active layer and a semiconductor layer of a second electrically-conductive type that are stacked in this order on a side surface and a top surface of the columnar crystalline structure; and a light-blocking member provided between the multiple columnar structures and having an inclined surface of less than 90 relative to the first surface.

A light-emitting device of an embodiment of the present disclosure includes: an insulating layer having a first surface and a second surface that are opposed to each other; multiple columnar structures each including a columnar crystalline structure of a first electrically-conductive type erected in a direction perpendicular to the first surface of the insulating layer, and an active layer and a semiconductor layer of a second electrically-conductive type that are stacked in this order on a side surface and a top surface of the columnar crystalline structure; and a light-blocking member provided between the multiple columnar structures and having an inclined surface of less than 90 relative to the first surface.

An object of the present invention is to provide a GaN crystal long in light emission lifetime by time-resolved photoluminescence measurement and provide high-quality GaN crystal and GaN substrate that have few specified crystal defects affecting the light emission lifetime. A gallium nitride crystal having a light emission lifetime by time-resolved photoluminescence measurement, of 5 ps or more and 200 ps or less, and satisfying at least one of the following requirement (i) and requirement (ii): (i) an FWHM in a 004 diffraction X-ray rocking curve is 50 arcsec or less at least one position of the crystal; and (ii) a dislocation density is 510.sup.6 cm.sup.2 or less.