Production method, production vessel and member for nitride crystal
View Patent ↗To provide a production method for a nitride crystal, where a nitride crystal can be prevented from precipitating in a portion other than on a seed crystal and the production efficiency of a gallium nitride single crystal grown on the seed crystal can be enhanced. In a method for producing a nitride crystal by an ammonothermal method in a vessel containing a mineralizer-containing solution, out of the surfaces of said vessel and a member provided in said vessel, at least a part of the portion coming into contact with said solution is constituted by a metal or alloy containing one or more atoms selected from the group consisting of tantalum (Ta), tungsten (W) and titanium (Ti), and has a surface roughness (Ra) of less than 1.80 μm.
1. A method for producing a nitride crystal, the method comprising:
charging a raw material of the nitride crystal and a mineralizer to a raw material dissolution region of a vessel;
placing a baffle plate having open pores in the vessel such that the vessel is divided into two regions consisting of the raw material dissolution region and a crystal growth region;
placing a seed crystal in the crystal growth region;
closing the vessel with an airtight seal;
charging the closed vessel with ammonia;
heating the sealed vessel to a temperature to form a solution of the mineralizer in ammonia;
growing the nitride crystal on the seed crystal in a subcritical or supercritical state;
wherein at least one of a surface portion of the vessel and a member provided in the vessel contacting the solution of the mineralizer in ammonia comprises a metal or alloy having one or more selected from the group consisting of tantalum (Ta), tungsten (W) and titanium (Ti), and
a surface roughness (Ra) of the surface portion contacting the saturated mineralizer solution is less than 1.80 μm.
2. The method for producing a nitride crystal as claimed in claim 1 , wherein the surface portion of the vessel comprising the metal or alloy having one or more selected from the group consisting of Ta, W and Ti is at least a part of the crystal growth region of the vessel.
3. The method for producing a nitride crystal as claimed in claim 2 , wherein 20% or more of the area of the surface of the crystal growth region comprises the metal or alloy.
4. The method for producing a nitride crystal as claimed in claim 1 , wherein the surface of a member provided in the vessel comprises the metal or alloy.
5. The method for producing a nitride crystal as claimed in claim 4 , wherein the member comprising the metal or alloy is disposed in the crystal growth region of the vessel.
6. The method for producing a nitride crystal as claimed in claim 1 , further comprising removal of oxygen from the vessel.
7. The method for producing a nitride crystal as claimed in claim 1 , wherein
the vessel is an inner cylinder disposed in an autoclave,
a space between the cylinder and an inner wall of the autoclave is free of oxygen, and
the nitride crystal is produced in the inner cylinder.