North Carolina State University

Hexatech, Inc.

Tokuyama Corporation

Tokyo University of Agriculture and Technology

Raoul Schlesser

Rafael F Dalmau

Zlatko Sitar

Baxter F Moody

Vladimir Noveski

David Henshall

Ramón R Collazo

Akinori Koukitu

Yoshinao Kumagai

Jinqiao Xie

Toru Kinoshita

Toru Nagashima

Ramon R Collazo

Yuki Kubota

Spalding Craft

The invention provides highly transparent single crystalline AlN layers as device substrates for light emitting diodes in order to improve the output and operational degradation of light emitting devices. The highly transparent single crystalline AlN layers have a refractive index in the a-axis direction in the range of 2.250 to 2.400 and an absorption coefficient less than or equal to 15 cm-1 at a wavelength of 265 nm. The invention also provides a method for growing highly transparent single crystalline AlN layers, the method including the steps of maintaining the amount of Al contained in wall deposits formed in a flow channel of a reactor at a level lower than or equal to 30% of the total amount of aluminum fed into the reactor, and maintaining the wall temperature in the flow channel at less than or equal to 1200&#xb0; C.

Highly transparent aluminum nitride single crystalline layers and devices made therefrom

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.

Polycrystalline aluminum nitride material and method of production thereof

Disclosed are methods and materials useful in the preparation of semiconductor devices. In particular embodiments, disclosed are methods for engineering polycrystalline aluminum nitride substrates that are thermally matched to further materials that can be combined therewith. For example, the polycrystalline aluminum nitride substrates can be engineered to have a coefficient of thermal expansion (CTE) that is closely matched to the CTE of a semiconductor material and/or to a material that can be used as a growth substrate for a semiconductor material. The invention also encompasses devices incorporating such thermally engineered substrates and semiconductor materials grown using such thermally engineered substrates. The thermally engineered substrates are advantageous for overcoming problems caused by damage arising from CTE mismatch between component layers in semiconductor preparation methods and materials.

Thermal expansion engineering for polycrystalline aluminum nitride sintered bodies

The present invention provides methods of preparing Group III-nitride films of controlled polarity and substrates coated with such controlled polarity films. In particular, the invention provides substrate preparation steps that optimize the substrate surface for facilitating growth of a Group III-polar film, an N-polar film, or a selectively patterned film with both a Group III-polar portion and an N-polar portion in precise positioning. The methods of the invention are particularly suited for use in CVD methods.

Controlled polarity group III-nitride films and methods of preparing such films

The invention provides a method of forming a dense, shaped article, such as a crucible, formed of a refractory material, the method comprising the steps of placing a refractory material having a melting point of at least about 2900&#xb0; C. in a mold configured to form the powder into an approximation of the desired shape. The mold containing the powder is treated at a temperature and pressure sufficient to form a shape-sustaining molded powder that conforms to the shape of the mold, wherein the treating step involves sintering or isostatic pressing. The shape-sustaining molded powder can be machined into the final desired shape and then sintered at a temperature and for a time sufficient to produce a dense, shaped article having a density of greater than about 90% and very low open porosity. Preferred refractory materials include tantalum carbide and niobium carbide.

Dense, shaped articles constructed of a refractory material and methods of preparing such articles

A method of growing bulk single crystals of an AlN on a single crystal seed is provided, wherein an AlN source material is placed within a crucible chamber in spacial relationship to a seed fused to the cap of the crucible. The crucible is heated in a manner sufficient to establish a temperature gradient between the source material and the seed with the seed at a higher temperature than the source material such that the outer layer of the seed is evaporated, thereby cleaning the seed of contaminants and removing any damage to the seed incurred during seed preparation. Thereafter, the temperature gradient between the source material and the seed is inverted so that the source material is sublimed and deposited on the seed, thereby growing a bulk single crystal of AlN.

Seeded growth process for preparing aluminum nitride single crystals

The invention provides a method of forming a dense, shaped article, such as a crucible, formed of a refractory material, the method comprising the steps of placing a refractory material having a melting point of at least about 2900&#xb0; C. in a mold configured to form the powder into an approximation of the desired shape. The mold containing the powder is treated at a temperature and pressure sufficient to form a shape-sustaining molded powder that conforms to the shape of the mold, wherein the treating step involves sintering or isostatic pressing. The shape-sustaining molded powder can be machined into the final desired shap and then sintered at a temperature and for a time sufficient to produce a dense, shaped article having a density of greater than about 90% and very low open porosity. Preferred refractory materials include tantalum carbide and niobium carbide.

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Cary, NC, United States of America

Raoul Schlesser