The present invention includes: transferring a C-plane sapphire thin film 1t having an off-angle of 0.5-5° onto a handle substrate composed of a ceramic material having a coefficient of thermal expansion at 800 K that is greater than that of silicon and less than that of C-plane sapphire; performing high-temperature nitriding treatment on the GaN epitaxial growth substrate 11 and covering the surface of the C-plane sapphire thin film 1t with a surface treatment layer 11a made of AlN; having GaN grow epitaxially on the surface treatment layer 11a; ion-implanting a GaN film 13; pasting and bonding together the GaN film-side surface of the ion-implanted GaN film carrier and a support substrate 12; performing peeling at an ion implantation region 13.sub.ion in the GaN film 13 and transferring a GaN thin film 13a onto the support substrate 12; and obtaining a GaN laminate substrate 10.

A gallium nitride vapor phase epitaxy apparatus capable of doping magnesium is provided. The apparatus is used in vapor phase epitaxy not using organic metal as a gallium raw material. The apparatus comprises a reactor vessel and a wafer holder. The apparatus comprises a first raw material gas supply pipe configured to supply a first raw material gas containing gallium. The apparatus comprises a second raw material gas supply pipe configured to supply a second raw material gas, which contains nitrogen and configured to react with the first raw material gas. The apparatus comprises a third raw material gas supply pipe configured to supply a third raw material gas containing magnesium. The third raw material gas supply pipe is configured capable of placing a magnesium-based oxide on its supply path. The apparatus comprises a first heating unit configured to heat the magnesium-based oxide in a first temperature range.

A crystal substrate 1 includes an underlying layer 2 and a thick film 3. The underlying layer 2 is composed of a crystal of a nitride of a group 13 element and includes a first main face 2a and a second main face 2b. The thick film 3 is composed of a crystal of a nitride of a group 13 element and provided over the first main face of the underlying layer. The underlying layer 2 includes a low carrier concentration region 5 and a high carrier concentration region 4 both extending between the first main face 2a and the second main face 2b.

A method of fabricating a heterostructure includes providing a substrate, and implementing a non-sputtered, epitaxial growth procedure at a growth temperature to form a wurtzite structure supported by the substrate. The wurtzite structure includes an alloy of gallium nitride. The non-sputtered, epitaxial growth procedure is configured to incorporate a group IIIB element into the alloy. The wurtzite structure exhibits a breakdown field strength greater than a ferroelectric coercive field strength of the wurtzite structure.

A nitride semiconductor laminate includes: a substrate comprising a group III nitride semiconductor and including a surface and a reverse surface, the surface being formed from a nitrogen-polar surface, the reverse surface being formed from a group III element-polar surface and being provided on the reverse side from the surface; a protective layer provided at least on the reverse surface side of the substrate and having higher heat resistance than the reverse surface of the substrate; and a semiconductor layer provided on the surface side of the substrate and comprising a group III nitride semiconductor. The concentration of O in the semiconductor layer is lower than 1×10.sup.17 at/cm.sup.3.

A free-standing substrate, for growing epitaxial crystal composed of a group 13 nitride crystal selected from gallium nitride, aluminum nitride, indium nitride or a mixed crystal thereof, includes a nitrogen polar surface and group 13 element polar surface. The nitrogen polar surface is warped in a convex shape, and a chamfer part is provided in an outer peripheral part of the nitrogen polar surface.

An AlN monocrystal plate disclosed herein may include: a first surface in a thickness direction; and a second surface opposing the first surface. A metal component containing region may be disposed substantially parallel to the first surface in an intermediate portion between the first surface and the second surface. In the metal component containing region, a plurality of metal components may be introduced and distributed. A type of the metal components may be Ga.

A group III-nitride laminated substrate includes a sapphire substrate, a first layer that is formed on the sapphire substrate and is made of aluminum nitride, a second layer that is formed on the first layer and serves as an n-type layer made of gallium nitride and doped with an n-type dopant, a third layer that is formed on the second layer and serves as a light-emitting layer made of a group III-nitride, and a fourth layer that is formed on the third layer and serves as a p-type layer made of a group III-nitride and doped with a p-type dopant. The second layer has a thickness of 7 μm or less. A half-value width of (0002) diffraction determined through X-ray rocking curve analysis is 100 seconds or less, and a half-value width of (10-12) diffraction determined through X-ray rocking curve analysis is 200 seconds or less.

An object is to provide a nonpolar or semipolar GaN substrate having improved size and crystal quality. A self-standing GaN substrate has an angle between the normal of the principal surface and an m-axis of 0 degrees or more and 20 degrees or less, wherein: the size of the projected image in a c-axis direction when the principal surface is vertically projected on an M-plane is 10 mm or more; and when an a-axis length is measured on an intersection line between the principal surface and an A-plane, a low distortion section with a section length of 6 mm or more and with an a-axis length variation within the section of 10.0×10.sup.−5 Å or less is observed.

According to the present invention, there is provided a group III nitride semiconductor substrate (free-standing substrate 30) that is formed of group III nitride semiconductor crystals. Both exposed first and second main surfaces in a relationship of top and bottom are semipolar planes. A variation coefficient of an emission wavelength of each of the first and second main surfaces, which is calculated by dividing a standard deviation of an emission wavelength by an average value of the emission wavelength, is 0.05% or less in photoluminescence (PL) measurement in which mapping is performed in units of an area of 1 mm.sup.2 by emitting helium-cadmium (He—Cd) laser, which has a wavelength of 325 nm and an output of 10 mW or more and 40 mW or less, at room temperature. In a case where devices are manufactured over the free-standing substrate 30, variations in quality among the devices are suppressed.