A method for producing a Group III nitride crystal includes: preparing a protective layer on a region except for an epitaxial growth surface of an RAMO.sub.4 substrate containing a single crystal represented by the general formula RAMO.sub.4 (wherein R represents one or a plurality of a trivaient element selected from a group of elements including: Sc, In, Y, and a lanthanoid element, A represents one or a plurality of a trivalent element selected from a group of elements including: Fe(III), Ga, and Al, and M represents one or a plurality of a divalent element selected from a group of elements including: Mg, Mn, Fe(II), Co, Cu, Zn, and Cd); and forming a Group III nitride crystal on the epitaxial growth surface of the RAMO.sub.4 substrate by a flux method.

A method for producing a Group III nitride crystal includes: preparing a protective layer on a region except for an epitaxial growth surface of an RAMO.sub.4 substrate containing a single crystal represented by the general formula RAMO.sub.4 (wherein R represents one or a plurality of a trivaient element selected from a group of elements including: Sc, In, Y, and a lanthanoid element, A represents one or a plurality of a trivalent element selected from a group of elements including: Fe(III), Ga, and Al, and M represents one or a plurality of a divalent element selected from a group of elements including: Mg, Mn, Fe(II), Co, Cu, Zn, and Cd); and forming a Group III nitride crystal on the epitaxial growth surface of the RAMO.sub.4 substrate by a flux method.

A method for producing a Group III nitride semiconductor includes feeding a nitrogen-containing gas into a molten mixture of a Group III metal and a flux placed in a furnace, to thereby grow a Group III nitride semiconductor on a seed substrate, wherein the Group III nitride semiconductor is grown on the seed substrate, while controlling the surface modification weight ratio, which is defined as the ratio of the weight of Na including a portion surface-modified through oxidation or hydroxidation to the weight of Na when the surface thereof has no surface-modified portion as a reference weight, with Na serving as the flux.

A method for producing a Group III nitride semiconductor includes feeding a nitrogen-containing gas into a molten mixture of a Group III metal and a flux placed in a furnace, to thereby grow a Group III nitride semiconductor on a seed substrate, wherein the Group III nitride semiconductor is grown on the seed substrate, while controlling the surface modification weight ratio, which is defined as the ratio of the weight of Na including a portion surface-modified through oxidation or hydroxidation to the weight of Na when the surface thereof has no surface-modified portion as a reference weight, with Na serving as the flux.

It is provided a method of growing a group 13 nitride crystal layer, on an underlying substrate including a seed crystal layer composed of a group 13 nitride. The underlying substrate is immersed in a melt containing a flux to grow a group 13 nitride crystal layer two-dimensionally on a nitrogen polar surface of the seed crystal layer by flux method.

A method for producing a Group III nitride crystal including preparing an RAMgO.sub.4 substrate containing a single crystal represented by the general formula RAMgO.sub.4 (wherein R represents one or a plurality of trivalent elements selected from the group consisting of Sc, In, Y, and a lanthanoid element, and A represents one or a plurality of trivalent elements selected from the group consisting of Fe(III), Ga, and Al); and growing a Group III nitride crystal containing Mg on the RAMgO.sub.4 substrate.

A method for producing a Group III nitride crystal including preparing an RAMgO.sub.4 substrate containing a single crystal represented by the general formula RAMgO.sub.4 (wherein R represents one or a plurality of trivalent elements selected from the group consisting of Sc, In, Y, and a lanthanoid element, and A represents one or a plurality of trivalent elements selected from the group consisting of Fe(III), Ga, and Al); and growing a Group III nitride crystal containing Mg on the RAMgO.sub.4 substrate.

There is provided a large-diameter Group-III element nitride semiconductor substrate including a first surface and a second surface, in which, despite its large diameter, variations in quality in the first surface are suppressed. A Group-III element nitride semiconductor includes: a first surface; and a second surface, wherein the Group-III element nitride semiconductor substrate has a diameter of 100 mm or more, and wherein the Group-III element nitride semiconductor substrate has a coefficient of variation of a yellow luminescence intensity in a range corresponding to 88% or more of an entire region of the first surface of 0.3 or less based on a photoluminescence spectrum obtained through photoluminescence measurement of a range of the entire region of the first surface.

A method of manufacturing a group-III nitride crystal includes: a seed crystal preparation step of preparing a plurality of dot-shaped group-III nitrides on a substrate as a plurality of seed crystals for growth of a group-III nitride crystal; and a crystal growth step of bringing surfaces of the seed crystals into contact with a melt containing an alkali metal and at least one group-III element selected from gallium, aluminum, and indium in an atmosphere containing nitrogen and thereby reacting the group-III element with the nitrogen in the melt to grow the group-III nitride crystal.

A method of manufacturing a group-III nitride crystal includes: a seed crystal preparation step of preparing a plurality of dot-shaped group-III nitrides on a substrate as a plurality of seed crystals for growth of a group-III nitride crystal; and a crystal growth step of bringing surfaces of the seed crystals into contact with a melt containing an alkali metal and at least one group-III element selected from gallium, aluminum, and indium in an atmosphere containing nitrogen and thereby reacting the group-III element with the nitrogen in the melt to grow the group-III nitride crystal.