Growth conditions and morphology of GaN single crystals fabricated by the Na flux method

Crystal growth of GaN was carried out by the Na flux method at 700-850°C and 1-5 MPa of N₂ for 200 h. At higher temperatures and lower pressures, only Na-Ga intermetallic compounds are formed. At higher pressures or lower temperatures, the morphology of GaN single crystals depends on the experimental conditions. Hexagonal platelet crystals were obtained at lower temperature and higher N₂ pressure, and hexagonal prismatic crystals grew at higher temperature and lower N₂ pressure. Colorless transparent prismatic single crystals with a size of 1.0 × 0.5 × 0.5 mm³ were synthesized by slowly increasing the growth temperature at a rate of 0.5°C/h from 750 to 800°C under 3 MPa of N₂.