Abstract: Bulk single crystal of aluminum nitride (AlN) having an a real planar defect density?100 cm?2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

Abstract: Semiconductor structures and devices based thereon include an aluminum nitride single-crystal substrate and at least one layer epitaxially grown thereover. The epitaxial layer may comprise at least one of AlN, GaN, InN, or any binary or tertiary alloy combination thereof, and have an average dislocation density within the semiconductor heterostructure is less than about 106 cm?2.

Abstract: In various embodiments, a semiconductor device includes an aluminum nitride single-crystal substrate, a pseudomorphic strained layer disposed thereover that comprises at least one of AlN, GaN, InN, or an alloy thereof, and, disposed over the strained layer, a semiconductor layer that is lattice-mismatched to the substrate and substantially relaxed.

Abstract: A method and apparatus for producing bulk single crystals of AlN having low dislocation densities of about 10,000 cm?2 or less includes a crystal growth enclosure with Al and N2 source material therein, capable of forming bulk crystals. The apparatus maintains the N2 partial pressure at greater than stoichiometric pressure relative to the Al within the crystal growth enclosure, while maintaining the total vapor pressure in the crystal growth enclosure at super-atmospheric pressure. At least one nucleation site is provided in the crystal growth enclosure, and provision is made for cooling the nucleation site relative to other locations in the crystal growth enclosure. The Al and N2 vapor is then deposited to grow single crystalline low dislocation density AlN at the nucleation site. High efficiency ultraviolet light emitting diodes and ultraviolet laser diodes are fabricated on low defect density AlN substrates, which are cut from the low dislocation density AlN crystals.

Abstract: In various embodiments, non-zero thermal gradients are formed within a growth chamber both substantially parallel and substantially perpendicular to the growth direction during formation of semiconductor crystals, where the ratio of the two thermal gradients (parallel to perpendicular) is less than 10, by, e.g., arrangement of thermal shields outside of the growth chamber.

Abstract: In various embodiments, a semiconductor device includes an aluminum nitride single-crystal substrate, a pseudomorphic strained layer disposed thereover that comprises at least one of AlN, GaN, InN, or an alloy thereof, and, disposed over the strained layer, a semiconductor layer that is lattice-mismatched to the substrate and substantially relaxed.

Abstract: Fabrication of doped and undoped stoichiometric polycrystalline AlN ceramics with high purity is accomplished by, for example, reacting Al pellets with nitrogen gas. Such polycrystalline AlN ceramics may be utilized in the fabrication of high purity AlN single crystals, which may be annealed to enhance a conductivity thereof.

Abstract: A method and apparatus for producing bulk single crystals of AlN having low dislocation densities of about 10,000 cm?2 or less includes a crystal growth enclosure with Al and N2 source material therein, capable of forming bulk crystals. The apparatus maintains the N2 partial pressure at greater than stoichiometric pressure relative to the Al within the crystal growth enclosure, while maintaining the total vapor pressure in the crystal growth enclosure at super-atmospheric pressure. At least one nucleation site is provided in the crystal growth enclosure, and provision is made for cooling the nucleation site relative to other locations in the crystal growth enclosure. The Al and N2 vapor is then deposited to grow single crystalline low dislocation density AlN at the nucleation site. High efficiency ultraviolet light emitting diodes and ultraviolet laser diodes are fabricated on low defect density AlN substrates, which are cut from the low dislocation density AlN crystals.

Abstract: In various embodiments, methods of forming single-crystal AlN include providing a substantially undoped polycrystalline AlN ceramic having an oxygen concentration less than approximately 100 ppm, forming a single-crystal bulk AlN crystal by a sublimation-recondensation process at a temperature greater than approximately 2000° C., and cooling the bulk AlN crystal to a first temperature between approximately 1500° C. and approximately 1800° C. at a first rate less than approximately 250° C./hour.

Abstract: A UV source is regulated according to one or more purification parameters to produce a desired germicidal effect in a liquid while minimizing wasted power.

Abstract: In various embodiments, a semiconductor device includes an aluminum nitride single-crystal substrate, a pseudomorphic strained layer disposed thereover that comprises at least one of AlN, GaN, InN, or an alloy thereof, and, disposed over the strained layer, a semiconductor layer that is lattice-mismatched to the substrate and substantially relaxed.

Abstract: A method and apparatus for producing bulk single crystals of AlN having low dislocation densities of about 10,000 cm?2 or less includes a crystal growth enclosure with Al and N2 source material therein, capable of forming bulk crystals. The apparatus maintains the N2 partial pressure at greater than stoichiometric pressure relative to the Al within the crystal growth enclosure, while maintaining the total vapor pressure in the crystal growth enclosure at super-atmospheric pressure. At least one nucleation site is provided in the crystal growth enclosure, and provision is made for cooling the nucleation site relative to other locations in the crystal growth enclosure. The Al and N2 vapor is then deposited to grow single crystalline low dislocation density AlN at the nucleation site. High efficiency ultraviolet light emitting diodes and ultraviolet laser diodes are fabricated on low defect density AlN substrates, which are cut from the low dislocation density AlN crystals.

Abstract: Fabrication of doped AlN crystals and/or AlGaN epitaxial layers with high conductivity and mobility is accomplished by, for example, forming mixed crystals including a plurality of impurity species and electrically activating at least a portion of the crystal.

Abstract: Semiconductor structures and devices based thereon include an aluminum nitride single-crystal substrate and at least one layer epitaxially grown thereover. The epitaxial layer may comprise at least one of AlN, GaN, InN, or any binary or tertiary alloy combination thereof, and have an average dislocation density within the semiconductor heterostructure is less than about 106 cm?2.

Abstract: Fabrication of doped AlN crystals and/or AlGaN epitaxial layers with high conductivity and mobility is accomplished by, for example, forming mixed crystals including a plurality of impurity species and electrically activating at least a portion of the crystal.

Abstract: Semiconductor structures and devices based thereon include an aluminum nitride single-crystal substrate and at least one layer epitaxially grown thereover. The epitaxial layer may comprise at least one of AlN, GaN, InN, or any binary or tertiary alloy combination thereof, and have an average dislocation density within the semiconductor heterostructure is less than about 106 cm?2.

Abstract: Semiconductor structures and devices based thereon include an aluminum nitride single-crystal substrate and at least one layer epitaxially grown thereover. The epitaxial layer may comprise at least one of AlN, GaN, InN, or any binary or tertiary alloy combination thereof, and have an average dislocation density within the semiconductor heterostructure is less than about 106 cm?2.

Abstract: Semiconductor structures are fabricated to include strained epitaxial layers exceeding a predicted critical thickness thereof.

Abstract: Bulk single crystal of aluminum nitride (AlN) having an a real planar defect density?100 cm?2 Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

Abstract: A crucible for growing III-nitride (e.g., aluminum nitride) single crystals is provided. The crucible includes an elongated wall structure defining an interior crystal growth cavity. Embodiments include a plurality of grains and a wall thickness of at least about 1.5 times the average grain size. In particular embodiments, the crucible includes first and second layers of grains the first layer including grains forming an inside surface thereof and the second layer being superposed with the first layer. The crucible may be fabricated from tungsten-rhenium (W—Re) alloys; rhenium (Re); tantalum monocarbide (TaC); tantalum nitride (Ta2N); hafnium nitride (HfN); a mixture of tungsten and tantalum (W—Ta); tungsten (W); and combinations thereof.