A silicon-based molten composition according to an exemplary embodiment is used for a solution growth method for forming a silicon carbide single crystal, and represented by Formula 1 including silicon (Si), a first metal M1, a second metal M2 and a third metal M3, wherein the first metal M1 is one or more selected from the group consisting of nickel (Ni) and manganese (Mn), the second metal M2 is one or more selected from the group consisting of scandium (Sc) and titanium (Ti), and the third metal M3 is one or more selected from the group consisting of aluminum (Al) and gallium (Ga):

Si.sub.aM1.sub.bM2.sub.cM3.sub.dFormula 1 wherein a is 0.3 to 0.8, b is 0.1 to 0.5, c is 0.01 to 0.3, d is 0.01 to 0.2, and a+b+c+d is 1.

A silicon-based molten composition according to an exemplary embodiment is used for a solution growth method for forming a silicon carbide single crystal, and represented by Formula 1 including silicon (Si), a first metal M1, a second metal M2 and a third metal M3, wherein the first metal M1 is one or more selected from the group consisting of nickel (Ni) and manganese (Mn), the second metal M2 is one or more selected from the group consisting of scandium (Sc) and titanium (Ti), and the third metal M3 is one or more selected from the group consisting of aluminum (Al) and gallium (Ga):

Si.sub.aM1.sub.bM2.sub.cM3.sub.dFormula 1 wherein a is 0.3 to 0.8, b is 0.1 to 0.5, c is 0.01 to 0.3, d is 0.01 to 0.2, and a+b+c+d is 1.

A self-supporting substrate includes a first nitride layer grown by a hydride vapor deposition method or ammonothermal method and comprising a nitride of one or more elements selected from the group consisting of gallium, aluminum and indium; and a second nitride layer grown by a sodium flux method on the first nitride layer and comprising a nitride of one or more elements selected from the group consisting of gallium, aluminum and indium. The first nitride layer includes a plurality of single crystal grains arranged therein and extending between a pair of main faces of the first nitride layer. The second nitride layer includes a plurality of single crystal grains arranged therein and extending between a pair of main faces of the second nitride layer. The first nitride layer has a thickness larger than a thickness of the second nitride layer.

A self-supporting substrate includes a first nitride layer grown by a hydride vapor deposition method or ammonothermal method and comprising a nitride of one or more elements selected from the group consisting of gallium, aluminum and indium; and a second nitride layer grown by a sodium flux method on the first nitride layer and comprising a nitride of one or more elements selected from the group consisting of gallium, aluminum and indium. The first nitride layer includes a plurality of single crystal grains arranged therein and extending between a pair of main faces of the first nitride layer. The second nitride layer includes a plurality of single crystal grains arranged therein and extending between a pair of main faces of the second nitride layer. The first nitride layer has a thickness larger than a thickness of the second nitride layer.

A n-type SiC single crystal with low resistivity and low threading dislocation density is provided, which is achieved by a n-type SiC single crystal containing germanium and nitrogen, wherein the density ratio of the germanium and the nitrogen [Ge/N] satisfies the relationship 0.17<[Ge/N]<1.60.

A n-type SiC single crystal with low resistivity and low threading dislocation density is provided, which is achieved by a n-type SiC single crystal containing germanium and nitrogen, wherein the density ratio of the germanium and the nitrogen [Ge/N] satisfies the relationship 0.17<[Ge/N]<1.60.

A method of producing a SiC single crystal includes: disposing a SiC seed crystal at a bottom part inside a graphite crucible; causing a solution containing Si, C and R (R is at least one selected from the rare earth elements inclusive of Sc and Y) or X (X is at least one selected from the group consisting of Al, Ge, Sn, and transition metals exclusive of Sc and Y) to be present in the crucible; supercooling the solution so as to cause the SiC single crystal to grow on the seed crystal; and adding powdery or granular Si and/or SiC raw material to the solution from above the graphite crucible while keeping the growth of the SiC single crystal.

A method of producing a SiC single crystal includes: disposing a SiC seed crystal at a bottom part inside a graphite crucible; causing a solution containing Si, C and R (R is at least one selected from the rare earth elements inclusive of Sc and Y) or X (X is at least one selected from the group consisting of Al, Ge, Sn, and transition metals exclusive of Sc and Y) to be present in the crucible; supercooling the solution so as to cause the SiC single crystal to grow on the seed crystal; and adding powdery or granular Si and/or SiC raw material to the solution from above the graphite crucible while keeping the growth of the SiC single crystal.

In one instance, the invention provides a bulk crystal of group III nitride having a thickness of more than 1 mm without cracking above the sides of a seed crystal. This bulk group III nitride crystal is expressed as Ga.sub.x1Al.sub.y1In.sub.1-x1-y1N (0x11, 0x1+y11) and the seed crystal is expressed as Ga.sub.x2Al.sub.y2In.sub.1-x2-y2N (0x21, 0x2+y21). The bulk crystal of group III nitride can be grown in supercritical ammonia or a melt of group III metal using at least one seed crystal having basal planes of c-orientation and sidewalls of m-orientation. By exposing only c-planes and m-planes in this instance, cracks originating from the sides of the seed crystal are avoided.

In one instance, the invention provides a bulk crystal of group III nitride having a thickness of more than 1 mm without cracking above the sides of a seed crystal. This bulk group III nitride crystal is expressed as Ga.sub.x1Al.sub.y1In.sub.1-x1-y1N (0x11, 0x1+y11) and the seed crystal is expressed as Ga.sub.x2Al.sub.y2In.sub.1-x2-y2N (0x21, 0x2+y21). The bulk crystal of group III nitride can be grown in supercritical ammonia or a melt of group III metal using at least one seed crystal having basal planes of c-orientation and sidewalls of m-orientation. By exposing only c-planes and m-planes in this instance, cracks originating from the sides of the seed crystal are avoided.