Abstract: The present disclosure provides a method for forming an aluminum nitride single crystalline substrate that includes growing an AlN single crystalline boule followed by cooling the AlN single crystalline boule in three phases including a first cooling phase from the crystal growth temperature to a first intermediate temperature of about 1900° C. to about 1800° C., a second cooling phase from the first intermediate temperature to a second intermediate temperature of about 1500° C. to about 1400° C., wherein the second cooling phase is characterized by a cooling rate of 5.0° C. per minute or less, and a third cooling phase from the second intermediate temperature to room temperature. Also provided is an aluminum nitride single crystalline substrate having a dimensionless figure of merit (FOM) of 0.4 or above and optoelectronic devices made therefrom.

Abstract: 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.

Abstract: 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.

Abstract: 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.

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: 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.

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: 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.

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: 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.

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 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.