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Morrisville, NC, United States

The invention provides an optoelectronic device adapted to emit ultraviolet light, including an aluminum nitride single crystalline substrate, wherein the dislocation density of the substrate is less than about 10


Methods of preparing polycrystalline aluminum nitride materials that have high density, high purity, and favorable surface morphology are disclosed. The methods generally comprises pressing aluminum nitride powders to form a slug, sintering the slug to form a sintered, polycrystalline aluminum nitride boule, and optionally shaping the boule and/or polishing at least a portion of the boule to provide a finished substrate. The sintered, polycrystalline aluminum nitride materials beneficially are prepared without the use of any sintering aid or binder, and the formed materials exhibit excellent density, AlN purity, and surface morphology.


Grant
Agency: Department of Defense | Branch: Missile Defense Agency | Program: STTR | Phase: Phase II | Award Amount: 500.00K | Year: 2004

Teh objective of the proposed work is to develop a process for the fabrication large-area aluminum nitride (AlN) wafers of up to 2" in diameter for III-nitride substrate applications. The growth process is based on a sublimation technique that utilizes adequately prepared SiC wafers as large-area seeds. A multi-step process developed in Phase I will be upscaled to larger area deposition, and will be tailored to (1) avoid SiC decomposition, (2) prepare the SiC seed surface for subsequent AlN deposition, and (3) to greatly reduce stress in the AlN single crystal. Boules will be oriented and cut into single crystalline wafers, which will be polished and, at later stages in the project, re-used as seeds.


The invention provides a power semiconductor device including an aluminum nitride single crystalline substrate, wherein the dislocation density of the substrate is less than about 10


Grant
Agency: Department of Defense | Branch: Missile Defense Agency | Program: STTR | Phase: Phase II | Award Amount: 600.00K | Year: 2002

"The objective of this proposal is the fabrication of AlN substrates with single crystalline quality meeting or exceeding the standards of commercially available SiC wafers. The growth process, which utilizes high temperature, subatmospheric pressure, and asteep temperature gradient, yields high-purity AlN single crystals at commercially interesting growth rates by sublimation of AlN in a nitrogen atmosphere. Through the proposed research, HexaTech, Inc. plans to increase the size of AlN bulk crystals,targeting the demonstration of 2" boule diameter, without compromising the crystal quality. Wafering and polishing will be performed at NCSU. The properties of grown crystals will be evaluated at NCSU and will include (1) microstructural analyses (opticaland scanning electron microscopies, x-ray diffraction, Raman spectroscopy), (2) chemical analysis (X-ray photoelectron spectroscopy), (3) identification of impurities (secondary ion mass spectroscopy, optical techniques), and (4) study of electricalproperties (I-V, Hall measurements). AlN wafers will find an immediate application as lattice-matched substrates for high-quality epitaxy of III-nitrides and will enable the fabrication of superior quality AlGaN electronic and optoelectronic devices,including high-frequency amplifiers and switches, blue and UV solid state lasers, solar-blind UV detectors, and surface acoustic wave (SAW) devices. Since the epitaxial processes and a variety of III-nitride device structures have been developed during thepast ten years on less favorable substrates with large lattice mismatch, the penetration of these new AlN wafers into the market place can occur without delay and to the immediate benefit of device performance."

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