Bulk GaN single crystal was grown by the flux growth. Using a flux, the solvent-thermal method for growing bulk GaN single crystal requires lower temperature (similar to 800 degrees C) and pressure (similar to 100 atm) than when growing them directly from high-temperature solution. In this study, we investigated the influence of the N-2 pressure and flux ratio on the growth of the bulk GaN single crystals and used 99% pure alkali metal as a flux. The mole fraction of flux/(flux+Ga) was 0.30-0.67. GaN single crystals were synthesized at a temperature of similar to 800 degrees C and an N-2 gas pressure of similar to 8 MPa for 200 h. The shape of the single crystals was examined by low magnification microscopy. The hexagonal struture of the GaN single crystals was confirmed by X-ray diffraction. The chemical composition was analyzed by electron probe micro analysis. The amounts of 02 and N2 impurities were analyzed by means of an N-2/O-2 determinator. The optical properties of the GaN single crystals were examined using a photoluminescence analyzer, in order to verify their suitability for blue emitting diodes. (c) 2006 Elsevier B.V. All rights reserved.