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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.

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

Dalmau R.,HexaTech | Moody B.,HexaTech | Xie J.,HexaTech | Collazo R.,North Carolina State University | Sitar Z.,North Carolina State University
Physica Status Solidi (A) Applications and Materials Science

The density and distribution of extended defects in AlN single crystals grown by physical vapor transport (PVT) was studied by bright field and polarized light microscopy, defect-selective etching, and high resolution X-ray diffraction (HRXRD). Etch pits associated with dislocation arrays forming low angle grain boundaries (LAGB) were observed and two types of LAGB were identified. Reduction of LAGB in AlN grown under reduced radial temperature gradients, as estimated by simulation of the growth cell, was demonstrated. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Bryan I.,North Carolina State University | Rice A.,North Carolina State University | Hussey L.,North Carolina State University | Bryan Z.,North Carolina State University | And 6 more authors.
Applied Physics Letters

Strain relaxation mechanisms were investigated in epitaxial AlN layers deposited on (0001)-oriented AlN substrates by metalorganic chemical vapor deposition. It was revealed that epitaxial AlN layers under tensile strain can exhibit micro-cracks and nano-pits. A correlation existed between the amount of strain and number of pits in localized areas. Pit densities as high as 10 10 cm-2 were observed in areas where the tensile strain reached ∼0.4%, while unstrained areas of the film showed step flow growth. These nano-pits occurred as a strain relaxation mechanism and were not related to intrinsic defects, such as threading dislocations or inversion domains. © 2013 American Institute of Physics. Source

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