Patent ID: 8420041

Claim:
A method for growing group III nitride crystals in a manner that exposes an alkali-metal mineralizer to minimal oxygen and moisture comprising; (a) loading group III-nitride seed crystals in a crystallization region of a high-pressure vessel and a group III-containing nutrient source in a nutrient region of the high-pressure vessel, the high-pressure vessel having a body defining a chamber containing said crystallization region and said nutrient region, and said high-pressure vessel having a clamp for sealing an end of the reactor, wherein the clamp is formed of precipitation hardenable Ni—Cr based superalloy having a grain flow in a radial direction in the clamp; (b) loading a metal-covered alkali metal mineralizer in the high-pressure vessel, wherein the metal-covered alkali metal mineralizer is formed by removing a surface oxide layer from the alkali metal mineralizer to expose a fresh surface of the mineralizer, and covering the fresh surface of the alkali metal mineralizer with a metal layer to form the metal-covered alkali metal mineralizer; (c) sealing the high-pressure vessel; (d) evacuating the high-pressure vessel to a pressure less than 1×10 −5 mbar; (e) filling the high-pressure vessel with ammonia; (f) ramping the temperature of the crystallization region above 500° C.; (g) maintaining the temperature condition described in (f) for sufficient time to grow crystals; (h) releasing ammonia to stop crystal growth; and (i) unsealing the high-pressure vessel.