A SiC ingot includes a core portion; and a surface layer that is formed on a plane of the core portion in a growing direction, and a coefficient of linear thermal expansion of the surface layer is smaller than a coefficient of linear thermal expansion of the core portion.

A method of measuring a SiC ingot includes a measuring step of measuring a curving direction of an atomic arrangement plane of a SiC single crystal at least along a first direction passing through a center in plan view and a second direction intersecting with the first direction to obtain a shape of the atomic arrangement plane; and a crystal growth step of performing crystal growth using the SiC single crystal as a seed crystal, in which in a case where the shape of the atomic arrangement plane measured in the measuring step is a saddle type, a crystal growth condition in the crystal growth step is set such that a convexity of a second growth front at the end of crystal growth becomes larger than a convexity of a first growth front when an amount of crystal growth in the center of the seed crystal is 7 mm.

In various embodiments, methods of forming single-crystal AlN include providing a substantially undoped polycrystalline AlN ceramic having an oxygen concentration less than approximately 100 ppm, forming a single-crystal bulk AlN crystal by a sublimation-recondensation process at a temperature greater than approximately 2000 C., and cooling the bulk AlN crystal to a first temperature between approximately 1500 C. and approximately 1800 C. at a first rate less than approximately 250 C./hour.

In a SiC substrate, when resistivities at a plurality of first measurement points that are in a region inside a boundary located 5 mm inward from an outer circumferential end thereof and that include a center and a plurality of measurement points separated by 10 mm from each other in the [11-20] direction or the [?1-120] direction from the center, and at two second measurement points that are located 1 mm inward from the outer circumferential end and located in each of the [11-20] direction from the center and the [?1-120] direction from the center are measured, a difference between the maximum resistivity and the minimum resistivity among the resistivities of each of the plurality of first measurement points and the two second measurement points is 0.5 m?.Math.cm or less, and the diameter is 149 mm or more.

In various embodiments, single-crystal aluminum nitride boules and substrates having high transparency to ultraviolet light and low defect density are formed. The single-crystal aluminum nitride may function as a platform for the fabrication of light-emitting devices such as light-emitting diodes and lasers.

In various embodiments, controlled heating and/or cooling conditions are utilized during the fabrication of aluminum nitride single crystals and aluminum nitride bulk polycrystalline ceramics. Thermal treatments may also be utilized to control properties of aluminum nitride crystals after fabrication.

A cobalt ferrite film consisting of twinned cobalt ferrite isomer crystals, metastable normal Co.sup.2+.sub.tet[Fe.sup.3+.sub.oct].sub.2O.sub.4 isomer [nCFO] and tetragonal inverted Fe.sup.3+.sub.tet[Co.sup.2+Fe.sup.3+].sub.octO.sup.4 isomer [iCFO], the nCFO and iCFO isomer crystals alternating in chessboard fashion in three dimensions, the cobalt ferrite film made by pulsed laser deposition in a vacuum chamber from a polycrystalline CoFe.sub.2O.sub.4 target on a single crystal one-side polished MgO substrate preferably heated to a temperature of greater than about 600? C.

A method of forming a film comprises growing, using a deposition system, at least a portion of the film and analyzing, using a RHEED instrument, the at least a portion of the film. Using a computer, data is acquired from the RHEED instrument that is indicative of a stoichiometry of the at least a portion of the film. Using the computer, adjustments to one or more process parameters of the deposition system are calculated to control stoichiometry of the film during subsequent deposition. Using the computer, instructions are transmitted to the deposition system to execute the adjustments of the one or more process parameters. Using the deposition system, the one or more process parameters are adjusted.

The present invention is aimed at providing a method of manufacturing a silicon carbide epitaxial wafer by which a plurality of silicon carbide epitaxial layers of a predetermined layer thickness can be precisely formed. In the present invention, a first n-type SiC epitaxial layer is formed on an n-type SiC substrate so that the rate of change in impurity concentration between the n-type SiC substrate and the first n-type SiC epitaxial layer will be greater than or equal to 20%. A second n-type SiC epitaxial layer is formed on the first n-type SiC epitaxial layer so that the rate of change in impurity concentration between the first n-type SiC epitaxial layer and the second n-type SiC epitaxial layer will be greater than or equal to 20%.

Provided are: a silicon carbide single crystal substrate which is cut out from a silicon carbide bulk single crystal grown by the Physical Vapor Transport method; and a process for producing the same. The number of screw dislocations in one of the semicircle areas of the substrate is smaller than that in the other thereof, namely, the number of screw dislocations in a given area of the substrate is reduced. The semicircle areas of the substrate correspond respectively to the halves of the substrate. The present invention pertains to: a silicon carbide single crystal substrate which is cut out from a silicon carbide bulk single crystal grown by the Physical Vapor Transport method and which is characterized in that the average value of the screw-dislocation densities observed at multiple measurement points in one of the semicircle areas, which correspond respectively to the halves of the substrate, is 80% or less of the average value of screw-dislocation densities observed at multiple measurement points in the other of the semicircle areas; and a process for producing the same.