There is provided a semiconductor substrate including: a sapphire substrate; an intermediate layer formed of gallium nitride with random crystal directions and provided on the sapphire substrate; and at least one or more semiconductor layers each of which is formed of a gallium nitride single crystal and that are provided on the intermediate layer.

There is provided a semiconductor substrate including: a sapphire substrate; an intermediate layer formed of gallium nitride with random crystal directions and provided on the sapphire substrate; and at least one or more semiconductor layers each of which is formed of a gallium nitride single crystal and that are provided on the intermediate layer.

A base substrate includes a supporting substrate comprising aluminum oxide, and a base crystal layer provided on a main face of the supporting substrate, comprising a crystal of a nitride of a group 13 element and having a crystal growth surface. At lease one of a metal of a group 13 element and a reaction product of a material of the supporting substrate and the crystal of the nitride of the group 13 element is present between the raised part and the supporting substrate. The reaction product contains at least aluminum and a group 13 element.

An object of the present invention is to provide a method for producing a group III nitride crystal in which generation of breaking or cracks is less likely to occur. To achieve the object, the method for producing a group III nitride crystal includes: seed crystal preparation including disposing a plurality of crystals of a group III nitride as a plurality of seed crystals on a substrate; and crystal growth including growing group III nitride crystals by contacting a surface of each of the seed crystals with a melt containing at least one group III element selected from gallium, aluminum, and indium and an alkali metal in an atmosphere containing nitrogen. In the seed crystal preparation, the plurality of seed crystals are disposed within a hexagonal region provided on the substrate.

There is provided a method for producing a gallium nitride crystal that can produce a gallium nitride crystal more efficiently, using liquid phase growth, the method for producing a gallium nitride crystal including: a step of adding at least one or more of a nitride of an alkali metal or an alkaline earth metal and a transition metal to metal gallium and iron nitride and performing heating in a nitrogen atmosphere to at least a reaction temperature at which the metal gallium reacts.

There is provided a method for producing a gallium nitride crystal that can produce a gallium nitride crystal more efficiently, using liquid phase growth, the method for producing a gallium nitride crystal including: a step of adding at least one or more of a nitride of an alkali metal or an alkaline earth metal and a transition metal to metal gallium and iron nitride and performing heating in a nitrogen atmosphere to at least a reaction temperature at which the metal gallium reacts.

A crystal of a group 13 nitride has an upper surface and lower surface and is composed of a crystal of a group 13 nitride selected from gallium nitride, aluminum nitride, indium nitride or the mixed crystals thereof. When the upper surface of the layer of the crystal of the group 13 nitride is observed by cathode luminescence, the upper surface includes a linear high-luminance light-emitting part and a low-luminance light-emitting region adjacent to the high-luminance light-emitting part. A half value width of reflection at the (0002) plane of a X-ray rocking curve on the upper surface is 3000 seconds or less and 20 seconds or more.

A method for growing a crystalline composition, the first crystalline composition may include gallium and nitrogen. The crystalline composition may have an infrared absorption peak at about 3175 cm.sup.−1, with an absorbance per unit thickness of greater than about 0.01 cm.sup.−1. In one embodiment, the composition ay have an amount of oxygen present in a concentration of less than about 3×10.sup.18 per cubic centimeter, and may be free of two-dimensional planar boundary defects in a determined volume of the first crystalline composition.

A method for growing a crystalline composition, the first crystalline composition may include gallium and nitrogen. The crystalline composition may have an infrared absorption peak at about 3175 cm.sup.−1, with an absorbance per unit thickness of greater than about 0.01 cm.sup.−1. In one embodiment, the composition ay have an amount of oxygen present in a concentration of less than about 3×10.sup.18 per cubic centimeter, and may be free of two-dimensional planar boundary defects in a determined volume of the first crystalline composition.

A layer of a crystal of a group 13 nitride selected from gallium nitride, aluminum nitride, indium nitride and the mixed crystals thereof has an upper surface and a bottom surface. The upper surface of the crystal layer of the group 13 nitride includes a linear high-luminance light-emitting part and a low-luminance light-emitting region adjacent to the high-luminance light-emitting part, observed by cathode luminescence. The high-luminance light-emitting part includes a portion extending along an m-plane of the crystal of the group 13 nitride.