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 degreesC and 1-5 MPa of N-2 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 N-2 pressure, and hexagonal prismatic crystals grew at higher temperature and lower N-2 pressure. Colorless transparent prismatic single crystals with a size of 1.0 x 0.5 x 0.5 mm(3) were synthesized by slowly increasing the growth temperature at a rate of 0.5 degreesC/h from 750 to 800 degreesC under 3 MPa of N-2.