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.

In some embodiments, an optoelectronic semiconductor light emitting device includes: a substrate; and a plurality of epitaxial semiconductor layers disposed on the substrate. Each of the epitaxial semiconductor layers can comprise an epitaxial oxide. At least one of the epitaxial semiconductor layers can comprise an optically emissive material of direct bandgap type. At least one of the epitaxial semiconductor layers can comprise (Al.sub.x1Ga.sub.1x1).sub.2O.sub.3 wherein 0x11. The plurality of epitaxial semiconductor layers can comprise: first region comprising a first conductivity type; a second region comprising a not-intentionally doped (NID) intrinsic region; and a third region comprising a second conductivity type. The substrate and the plurality of epitaxial semiconductor layers can be a substantially single crystal epitaxially formed device. The optoelectronic semiconductor light emitting device can be configured to emit light having a wavelength in a range from 150 nm to 425 nm.

In some embodiments, an optoelectronic semiconductor light emitting device includes: a substrate; and a plurality of epitaxial semiconductor layers disposed on the substrate. Each of the epitaxial semiconductor layers can comprise an epitaxial oxide. At least one of the epitaxial semiconductor layers can comprise an optically emissive material of direct bandgap type. At least one of the epitaxial semiconductor layers can comprise (Al.sub.x1Ga.sub.1x1).sub.2O.sub.3 wherein 0x11. The plurality of epitaxial semiconductor layers can comprise: first region comprising a first conductivity type; a second region comprising a not-intentionally doped (NID) intrinsic region; and a third region comprising a second conductivity type. The substrate and the plurality of epitaxial semiconductor layers can be a substantially single crystal epitaxially formed device. The optoelectronic semiconductor light emitting device can be configured to emit light having a wavelength in a range from 150 nm to 425 nm.

The techniques described herein relate to a transistor, including a substrate including SiC-4H, MgO, or AlGaO.sub.3; an epitaxial channel layer on the substrate, and a gate layer on the epitaxial channel layer. The epitaxial channel layer can include Ga.sub.2O.sub.3 with a first bandgap, wherein the Ga.sub.2O.sub.3 is: -Ga.sub.2O.sub.3 with a hexagonal or trigonal crystal symmetry; -Ga.sub.2O.sub.3 with an orthorhombic crystal symmetry; or -Ga.sub.2O.sub.3 with a cubic crystal symmetry. The gate layer can include an oxide material with a second bandgap, where the second bandgap is wider than the first bandgap. The transistor can also include electrical contacts including: a source electrical contact coupled to the epitaxial channel layer; a drain electrical contact coupled to the epitaxial channel layer; and a gate electrical contact coupled to the gate layer.

The techniques described herein relate to a transistor, including a substrate including SiC-4H, MgO, or AlGaO.sub.3; an epitaxial channel layer on the substrate, and a gate layer on the epitaxial channel layer. The epitaxial channel layer can include Ga.sub.2O.sub.3 with a first bandgap, wherein the Ga.sub.2O.sub.3 is: -Ga.sub.2O.sub.3 with a hexagonal or trigonal crystal symmetry; -Ga.sub.2O.sub.3 with an orthorhombic crystal symmetry; or -Ga.sub.2O.sub.3 with a cubic crystal symmetry. The gate layer can include an oxide material with a second bandgap, where the second bandgap is wider than the first bandgap. The transistor can also include electrical contacts including: a source electrical contact coupled to the epitaxial channel layer; a drain electrical contact coupled to the epitaxial channel layer; and a gate electrical contact coupled to the gate layer.

A light-emitting element includes: an anode and a cathode; and a quantum dot layer positioned between the anode and the cathode, the quantum dot layer including a first quantum dot and a second quantum dot. The quantum dot layer includes a crystalline body serving as a core of the first quantum dot, and an inorganic amorphous material formed at at least a part of a surface of the crystalline body.

A light-emitting element includes: an anode and a cathode; and a quantum dot layer positioned between the anode and the cathode, the quantum dot layer including a first quantum dot and a second quantum dot. The quantum dot layer includes a crystalline body serving as a core of the first quantum dot, and an inorganic amorphous material formed at at least a part of a surface of the crystalline body.

A monolithic LED array precursor comprising a plurality of LED structures sharing a first semiconductor layer, wherein the first semiconductor layer defines a plane of the LED array precursor, each LED structure comprising (i) a second semiconductor layer on the first semiconductor layer, having an upper surface portion parallel to the plane of the LED array precursor, the second semiconductor layer having a regular trapezoidal cross-section normal to the upper surface portion, such that the second semiconductor layer has sloped sides, (ii) a third semiconductor layer on the second semiconductor layer, having an upper surface portion parallel to the plane of the LED array precursor, the third semiconductor layer having a regular trapezoidal cross-section normal to the upper surface portion, such that the third semiconductor layer has sloped sides parallel to the sloped sides of the second semiconductor layer, (iii) a fourth semiconductor layer on the third semiconductor layer, having an upper surface portion parallel to the plane of the LED array precursor, the fourth semiconductor layer having a regular trapezoidal cross-section normal to the upper surface portion, such that the fourth semiconductor layer has sloped sides parallel to the sloped sides of the third semiconductor layer, (iv) a primary electrical contact on the fourth semiconductor layer, wherein the contact is only on the upper surface portion of the fourth semiconductor layer which is parallel to the plane of the LED array precursor, (v) electrically insulating, optically transparent spacers on the sloped sides of the fourth semiconductor layer, the spacers having an internal surface facing the sloped sides of the fourth semiconductor layer and an opposing external surface and (vi) a reflecting layer, electrically conducting extending over the external surface of the spacers, wherein the third semiconductor layer comprises a plurality of quantum well sub-layers, the quantum well sub-layers having a greater thickness on a portion parallel to the plane of the LED array precursor and a reduced thickness on a portion which is not parallel to the plane of the LED array precursor.

A monolithic LED array precursor comprising a plurality of LED structures sharing a first semiconductor layer, wherein the first semiconductor layer defines a plane of the LED array precursor, each LED structure comprising (i) a second semiconductor layer on the first semiconductor layer, having an upper surface portion parallel to the plane of the LED array precursor, the second semiconductor layer having a regular trapezoidal cross-section normal to the upper surface portion, such that the second semiconductor layer has sloped sides, (ii) a third semiconductor layer on the second semiconductor layer, having an upper surface portion parallel to the plane of the LED array precursor, the third semiconductor layer having a regular trapezoidal cross-section normal to the upper surface portion, such that the third semiconductor layer has sloped sides parallel to the sloped sides of the second semiconductor layer, (iii) a fourth semiconductor layer on the third semiconductor layer, having an upper surface portion parallel to the plane of the LED array precursor, the fourth semiconductor layer having a regular trapezoidal cross-section normal to the upper surface portion, such that the fourth semiconductor layer has sloped sides parallel to the sloped sides of the third semiconductor layer, (iv) a primary electrical contact on the fourth semiconductor layer, wherein the contact is only on the upper surface portion of the fourth semiconductor layer which is parallel to the plane of the LED array precursor, (v) electrically insulating, optically transparent spacers on the sloped sides of the fourth semiconductor layer, the spacers having an internal surface facing the sloped sides of the fourth semiconductor layer and an opposing external surface and (vi) a reflecting layer, electrically conducting extending over the external surface of the spacers, wherein the third semiconductor layer comprises a plurality of quantum well sub-layers, the quantum well sub-layers having a greater thickness on a portion parallel to the plane of the LED array precursor and a reduced thickness on a portion which is not parallel to the plane of the LED array precursor.

A light emitting element includes: a first semiconductor layer including a semiconductor of a first type; a second semiconductor layer including a semiconductor of a second type different from the first type; and an active layer between the first and second semiconductor layers, the active layer including a first active area including a first well layer, and a second active area including a second well layer. The first well layer has a first band gap, and the second well layer has a second band gap smaller than the first band gap. At least a portion of the first active area is between the second active area and the second semiconductor layer. A distance between the second active area and the second semiconductor layer is equal to or greater than 0.1 times of a distance between the first and second semiconductor layers.