A method for producing a SiC substrate with an epitaxial layer, which can prevent inventory of wafers from unduly increasing and wasteful production, is provided. This is achieved by a method for producing a SiC substrate with an epitaxial layer one at a time, the method comprising growing an epitaxial layer and growing a SiC substrate on a seed crystal substrate, and the method further comprising removing the obtained SiC substrate with the epitaxial layer from the seed crystal substrate.

In the present invention, a crucible formed of SiC as a main component is used as a container for a SiC solution. The SiC crucible is heated such that, for example, an isothermal line representing a temperature distribution within the crucible draws an inverted convex shape; and Si and C, which are derived from a main component SiC of the crucible, are eluted from a high-temperature surface region of the crucible in contact with the SiC solution, into the SiC solution, thereby suppressing precipitation of a SiC polycrystal on a surface of the crucible in contact with the SiC solution. To the SiC solution of this state, a SiC seed crystal is moved down from the upper portion of the crucible closer to the SiC solution and brought into contact with the SiC solution to grow a SiC single crystal on the SiC seed crystal.

In the present invention, a crucible formed of SiC as a main component is used as a container for a SiC solution. The SiC crucible is heated such that, for example, an isothermal line representing a temperature distribution within the crucible draws an inverted convex shape; and Si and C, which are derived from a main component SiC of the crucible, are eluted from a high-temperature surface region of the crucible in contact with the SiC solution, into the SiC solution, thereby suppressing precipitation of a SiC polycrystal on a surface of the crucible in contact with the SiC solution. To the SiC solution of this state, a SiC seed crystal is moved down from the upper portion of the crucible closer to the SiC solution and brought into contact with the SiC solution to grow a SiC single crystal on the SiC seed crystal.

An apparatus for producing SiC single crystals where the quality of the SiC single crystals is improved, and a production method using such an apparatus are provided. The apparatus for producing SiC single crystals according to an embodiment of the present invention is employed to produce an SiC single crystal by the solution growth method. The production apparatus includes a crucible and a support shaft. The crucible accommodates an SiC solution. The support shaft supports the crucible. The support shaft includes a heat removing portion for removing heat from a bottom portion of the crucible. The heat removing portion includes one of (a) a contact portion having a thermal conductivity not less than that of the bottom portion and contacting at least a portion of the bottom portion and (b) a space adjacent to at least a portion of the contact portion or the bottom portion.

An apparatus for producing SiC single crystals where the quality of the SiC single crystals is improved, and a production method using such an apparatus are provided. The apparatus for producing SiC single crystals according to an embodiment of the present invention is employed to produce an SiC single crystal by the solution growth method. The production apparatus includes a crucible and a support shaft. The crucible accommodates an SiC solution. The support shaft supports the crucible. The support shaft includes a heat removing portion for removing heat from a bottom portion of the crucible. The heat removing portion includes one of (a) a contact portion having a thermal conductivity not less than that of the bottom portion and contacting at least a portion of the bottom portion and (b) a space adjacent to at least a portion of the contact portion or the bottom portion.

[Object] To provide a production method capable of producing a gallium nitride crystal at a lower pressure. [Solution] Provided is a method for producing a gallium nitride crystal, the method including a step of heating metal gallium and iron nitride in a nitrogen atmosphere at least to a reaction temperature at which the metal gallium and the iron nitride react.

[Object] To provide a production method capable of producing a gallium nitride crystal at a lower pressure. [Solution] Provided is a method for producing a gallium nitride crystal, the method including a step of heating metal gallium and iron nitride in a nitrogen atmosphere at least to a reaction temperature at which the metal gallium and the iron nitride react.

A method for growing a periodically-poled nonlinear crystal may include placing a seed crystal into a melt to form a seed crystal melt mixture, where the seed crystal may include at least one of strontium tetraborate (SBO) or lithium triborate (LBO), and where the melt includes at least one of a mixture of Sr, B, and O or a mixture of Li, B, and O. The method may further include heating the seed crystal melt mixture to a predetermined temperature until the periodically-poled nonlinear crystal forms.

A method for growing a periodically-poled nonlinear crystal may include placing a seed crystal into a melt to form a seed crystal melt mixture, where the seed crystal may include at least one of strontium tetraborate (SBO) or lithium triborate (LBO), and where the melt includes at least one of a mixture of Sr, B, and O or a mixture of Li, B, and O. The method may further include heating the seed crystal melt mixture to a predetermined temperature until the periodically-poled nonlinear crystal forms.

A method for producing Si ingot single crystal including a Si ingot single crystal growing step, a temperature gradient controlling step and a continuous growing step is provided. In the growing step, the Si ingot single crystal is grown in silicon melt in crucible, and the growing step includes providing a low-temperature region in the Si melt and providing a silicon seed to contact the melt surface of the silicon melt to start crystal growth, and silicon single crystal grows along the melt surface of the silicon melt and toward the inside of the silicon melt. In the temperature gradient controlling step, the under-surface temperature gradient of the silicon single crystal is G1, the above-surface temperature gradient of the silicon single crystal is G2, G1 and G2 satisfy: G2/G1<6. The step of controlling the temperature gradient of silicon single crystal is repeated to obtain the Si ingot single crystal.