Abstract: A method of making a Group III nitride material that includes: providing a substrate; patterning a template on the substrate; depositing a layer of a material comprising aluminum, gallium and nitrogen on the substrate at a temperature; annealing the layer comprising aluminum, gallium and nitrogen; epitaxially growing Distributed Bragg Reflectors to form a structure on the substrate that comprises microcavities; and etching micropillars in the structure for at least 30 seconds with a heated basic solution is described.

Abstract: 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° C.

Abstract: The energy of formation of a point defect in a compound semiconductor is a function of the process conditions and the Fermi energy (the energy of the charge carriers). In wide bandgap semiconductors or insulators, the contribution of this energy to the formation energy of charged point defects is significant. For doping for n- or p-type conductivity, the larger the energy gap, the higher the concentration of compensating point defects that is at equilibrium with the system. This is a fundamental problem with wide bandgap materials that will be directly addressed with these capabilities. In this approach, minority carrier injection is used to modify the quasi-Fermi level to control the formation energy of the point defects. Increasing the formation energy of unwanted point defect through an external excitation that leads to excess minority carriers during the growth of the semiconductor device structure leads to a reduction in compensating point defects.

Abstract: 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 A1N 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° C.

Abstract: The present invention provides methods of protecting a surface of an aluminum nitride substrate. The substrate with the protected surface can be stored for a period of time and easily activated to be in a condition ready for thin film growth or other processing. In certain embodiments, the method of protecting the substrate surface comprises forming a passivating layer on at least a portion of the substrate surface by performing a wet etch, which can comprise the use of one or more organic compounds and one or more acids. The invention also provides aluminum nitride substrates having passivated surfaces.

Abstract: 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.

Abstract: 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° 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.

Abstract: The present invention provides methods of protecting a surface of an aluminum nitride substrate. The substrate with the protected surface can be stored for a period of time and easily activated to be in a condition ready for thin film growth or other processing. In certain embodiments, the method of protecting the substrate surface comprises forming a passivating layer on at least a portion of the substrate surface by performing a wet etch, which can comprise the use of one or more organic compounds and one or more acids. The invention also provides aluminum nitride substrates having passivated surfaces.

Abstract: The present invention provides methods of protecting a surface of an aluminum nitride substrate. The substrate with the protected surface can be stored for a period of time and easily activated to be in a condition ready for thin film growth or other processing. In certain embodiments, the method of protecting the substrate surface comprises forming a passivating layer on at least a portion of the substrate surface by performing a wet etch, which can comprise the use of one or more organic compounds and one or more acids. The invention also provides aluminum nitride substrates having passivated surfaces.

Abstract: The present invention provides methods of protecting a surface of an aluminum nitride substrate. The substrate with the protected surface can be stored for a period of time and easily activated to be in a condition ready for thin film growth or other processing. In certain embodiments, the method of protecting the substrate surface comprises forming a passivating layer on at least a portion of the substrate surface by performing a wet etch, which can comprise the use of one or more organic compounds and one or more acids. The invention also provides aluminum nitride substrates having passivated surfaces.

Abstract: The present invention provides methods of protecting a surface of an aluminum nitride substrate. The substrate with the protected surface can be stored for a period of time and easily activated to be in a condition ready for thin film growth or other processing. In certain embodiments, the method of protecting the substrate surface comprises forming a passivating layer on at least a portion of the substrate surface by performing a wet etch, which can comprise the use of one or more organic compounds and one or more acids. The invention also provides aluminum nitride substrates having passivated surfaces.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: The present invention provides methods of protecting a surface of an aluminum nitride substrate. The substrate with the protected surface can be stored for a period of time and easily activated to be in a condition ready for thin film growth or other processing. In certain embodiments, the method of protecting the substrate surface comprises forming a passivating layer on at least a portion of the substrate surface by performing a wet etch, which can comprise the use of one or more organic compounds and one or more acids. The invention also provides aluminum nitride substrates having passivated surfaces.

Abstract: 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° 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.

Abstract: 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° 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.

Abstract: 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.

Abstract: 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° 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.

Abstract: 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.