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.

In the present invention, in producing a SiC single crystal in accordance with a solution method, a crucible containing SiC as a main component and having an oxygen content of 100 ppm or less is used as the crucible to be used as a container for a Si—C solution. In another embodiment, a sintered body containing SiC as a main component and having an oxygen content of 100 ppm or less is placed in the crucible to be used as a container for a Si—C solution. The SiC crucible and SiC sintered body are obtained by molding and baking a SiC raw-material powder having an oxygen content of 2000 ppm or less. SiC, which is the main component of these, serves as a source for Si and C and allows Si and C to elute into the Si—C solution by heating.

In the present invention, in producing a SiC single crystal in accordance with a solution method, a crucible containing SiC as a main component and having an oxygen content of 100 ppm or less is used as the crucible to be used as a container for a Si—C solution. In another embodiment, a sintered body containing SiC as a main component and having an oxygen content of 100 ppm or less is placed in the crucible to be used as a container for a Si—C solution. The SiC crucible and SiC sintered body are obtained by molding and baking a SiC raw-material powder having an oxygen content of 2000 ppm or less. SiC, which is the main component of these, serves as a source for Si and C and allows Si and C to elute into the Si—C solution by heating.

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.

It is an object of the present invention to provide a silicon carbide substrate having a low defect density that does not contaminate a process device and a silicon carbide semiconductor device including the silicon carbide substrate. A silicon carbide substrate according to the present invention is a silicon carbide substrate including: a substrate inner portion; and a substrate outer portion surrounding the substrate inner portion, wherein non-dopant metal impurity concentration of the substrate inner portion is 1×10.sup.16 cm.sup.−3 or more, and a region of the substrate outer portion at least on a surface side thereof is a substrate surface region in which the non-dopant metal impurity concentration is less than 1×10.sup.16 cm.sup.−3.

A method for a SiC single crystal that allow prolonged growth to be achieved are provided. A method for producing a SiC single crystal in which a seed crystal substrate held on a seed crystal holding shaft is contacted with a Si—C solution having a temperature gradient such that a temperature of the Si—C solution decreases from an interior of the Si—C solution toward a liquid level of the Si—C solution, in a graphite crucible, to grow a SiC single crystal, wherein the method comprises the steps of: electromagnetic stirring of the Si—C solution with an induction coil to produce a flow, and heating of a lower part of the graphite crucible with a resistance heater.

A method for a SiC single crystal that allow prolonged growth to be achieved are provided. A method for producing a SiC single crystal in which a seed crystal substrate held on a seed crystal holding shaft is contacted with a Si—C solution having a temperature gradient such that a temperature of the Si—C solution decreases from an interior of the Si—C solution toward a liquid level of the Si—C solution, in a graphite crucible, to grow a SiC single crystal, wherein the method comprises the steps of: electromagnetic stirring of the Si—C solution with an induction coil to produce a flow, and heating of a lower part of the graphite crucible with a resistance heater.

A 4H-SiC single crystal having good morphology while preventing heterogeneous polymorphs from being mixed in regardless of the presence or absence of doping in growing a 4H-SiC single crystal by the TSSG method is obtained. When the off-angle on the grown crystal in a method for producing a SiC single crystal by a TSSG method is set to 60 to 68, heterogeneous polymorphs are less likely to be mixed in during the growth of 4H-SiC single crystal, and if, during that period, a meltback method is used to smooth the surface of the seed crystal and then grow the crystal, it is possible to obtain a grown crystal having good morphology.

The present invention reduces warpage of a Group III nitride semiconductor crystal in a method for producing a Group III nitride semiconductor crystal on a seed substrate through a flux method. A Group III nitride semiconductor is grown so that the total Al amount at the interface is not more than 310.sup.14/cm.sup.2, and the total Si amount at the interface is not more than 510.sup.14/cm.sup.2. Here, the total amount at the interface refers to a total number of atoms per unit area of an interface between the grown Group III nitride semiconductor and the seed substrate. Thus, warpage can be reduced by growing a Group III nitride semiconductor through a flux method.

The present invention reduces warpage of a Group III nitride semiconductor crystal in a method for producing a Group III nitride semiconductor crystal on a seed substrate through a flux method. A Group III nitride semiconductor is grown so that the total Al amount at the interface is not more than 310.sup.14/cm.sup.2, and the total Si amount at the interface is not more than 510.sup.14/cm.sup.2. Here, the total amount at the interface refers to a total number of atoms per unit area of an interface between the grown Group III nitride semiconductor and the seed substrate. Thus, warpage can be reduced by growing a Group III nitride semiconductor through a flux method.