Abstract: There is provided an epitaxial substrate, including: a GaN substrate whose main surface is a c-plane; and a GaN layer epitaxially grown on the main surface, wherein the main surface includes a region where an off-angle is 0.4° or more, and an E3 trap concentration in the GaN layer grown on the region is 3.0×1013 cm?3 or less.

Abstract: There is provided a nitride semiconductor substrate, including: a substrate configured as an n-type semiconductor substrate; and a drift layer provided on the substrate and configured as a gallium nitride layer containing donors and carbons, wherein a concentration of the donors in the drift layer is 5.0×1016/cm3 or less, and is equal to or more than a concentration of the carbons that function as acceptors in the drift layer, over an entire area of the drift layer, and a difference obtained by subtracting the concentration of the carbons that function as acceptors in the drift layer from the concentration of the donors in the drift layer, is gradually decreased from a substrate side toward a surface side of the drift layer.

Abstract: There is provided a nitride semiconductor substrate, including: a substrate configured as an n-type semiconductor substrate; and a drift layer provided on the substrate and configured as a gallium nitride layer containing donors and carbons, wherein a concentration of the donors in the drift layer is 5.0×1016/cm3 or less, and is equal to or more than a concentration of the carbons that function as acceptors in the drift layer, over an entire area of the drift layer, and a difference obtained by subtracting the concentration of the carbons that function as acceptors in the drift layer from the concentration of the donors in the drift layer, is gradually increased from a substrate side toward a surface side of the drift layer.

Abstract: There is provided a nitride semiconductor substrate, including: a substrate configured as an n-type semiconductor substrate; and a drift layer provided on the substrate and configured as a gallium nitride layer containing donors and carbons, wherein a concentration of the donors in the drift layer is 5.0×106 / cm3 or less, and is equal to or more than a concentration of the carbons that function as acceptors in the drift layer, over an entire area of the drift layer, and a difference obtained by subtracting the concentration of the carbons that function as acceptors in the drift layer from the concentration of the donors in the drift layer, is gradually increased from a substrate side toward a surface side of the drift layer.

Abstract: There is provided a nitride semiconductor substrate, including: a substrate configured as an n-type semiconductor substrate; and a drift layer provided on the substrate and configured as a gallium nitride layer containing donors and carbons, wherein a concentration of the donors in the drift layer is 5.0×1016/cm3 or less, and is equal to or more than a concentration of the carbons that function as acceptors in the drift layer, over an entire area of the drift layer, and a difference obtained by subtracting the concentration of the carbons that function as acceptors in the drift layer from the concentration of the donors in the drift layer, is gradually decreased from a substrate side toward a surface side of the drift layer.

Abstract: A nitride semiconductor epitaxial wafer includes a substrate, a GaN layer provided over the substrate, and an AlGaN layer provided over the GaN layer. The GaN layer has a wurtzite crystal structure, and a ratio c/a of a lattice constant c in a c-axis orientation of the GaN layer to a lattice constant a in an a-axis orientation of the GaN layer is not more than 1.6266.

Abstract: A nitride semiconductor epitaxial wafer includes a substrate, a GaN layer provided over the substrate, and an AlGaN layer provided over the GaN layer. The GaN layer has a wurtzite crystal structure, and a ratio c/a of a lattice constant c in a c-axis orientation of the GaN layer to a lattice constant a in an a-axis orientation of the GaN layer is not more than 1.6266.

Abstract: A nitride semiconductor epitaxial wafer includes a substrate, a GaN layer provided over the substrate, and an AlGaN layer provided over the GaN layer. The GaN layer has a wurtzite crystal structure, and a ratio c/a of a lattice constant c in a c-axis orientation of the GaN layer to a lattice constant a in an a-axis orientation of the GaN layer is not more than 1.6266.

Abstract: A nitride semiconductor epitaxial wafer includes a substrate, and a nitride semiconductor layer formed on the substrate, the nitride semiconductor layer including a (002) plane in an upper surface thereof. An in-plane dispersion of a full width half maximum (FWHM) of an X-ray rocking curve in the (002) plane or a (100) plane of the nitride semiconductor layer is not more than 30%. The wafer is not less than 100 ?m in thickness and not less than 50 mm in diameter.

Abstract: A nitride semiconductor epitaxial wafer includes a substrate, and a nitride semiconductor layer formed on the substrate, the nitride semiconductor layer including a (002) plane in an upper surface thereof. An in-plane dispersion of a full width half maximum (FWHM) of an X-ray rocking curve in the (002) plane or a (100) plane of the nitride semiconductor layer is not more than 30%. The wafer is not less than 100 ?m in thickness and not less than 50 mm in diameter.