HIGH-PRESSURE VESSEL FOR GROWING GROUP III NITRIDE CRYSTALS AND METHOD OF GROWING GROUP III NITRIDE CRYSTALS USING HIGH-PRESSURE VESSEL AND GROUP III NITRIDE CRYSTAL

摘要

Present invention discloses a high-pressure vessel of large size formed with a limited size of e.g. Ni—Cr based precipitation hardenable superalloy. Vessel may have multiple zones.;For instance, the high-pressure vessel may be divided into at least three regions with flow-restricting devices and the crystallization region is set higher temperature than other regions. This structure helps to reliably seal both ends of the high-pressure vessel, at the same time, may help to greatly reduce unfavorable precipitation of group III nitride at the bottom of the vessel.;Invention also discloses novel procedures to grow crystals with improved purity, transparency and structural quality. Alkali metal-containing mineralizers are charged with minimum exposure to oxygen and moisture until the high-pressure vessel is filled with ammonia. Several methods to reduce oxygen contamination during the process steps are presented. Back etching of seed crystals and a new temperature ramping scheme to improve structural quality are disclosed.