Single crystal growth of gallium nitride by slow-cooling of its congruent melt under high pressure

Saito, Hiroyuki; Utsumi, Wataru; Kaneko, Hiroshi*; Kiriyama, Koji*; Aoki, Katsutoshi

Single crystals of GaN were successfully synthesized by slowly cooling its stoichiometric melt under high pressure. Applying high pressures above 6.0 GPa prevented decomposition and allowed the congruent melt of GaN at 2220C, which was confirmed by an in situ X-ray diffraction study. Using a cubic-anvil-type, large volume, high-pressure apparatus and a GaN powder as a starting material, single crystal growth was achieved by reducing the temperature from 2400C at 6.5 GPa. The X-ray rocking curve of the recovered sample showed a very narrow line width, less than 30 arcsec, suggesting a low dislocation density. Bulk specimens of AlGaN alloys, which covered a composition range of 0x1 were also synthesized under high pressures.