Highly crystalline gallium nitride (GaN) single crystals with good luminescence property were grown at 1200 degrees C for 2 h by the reaction between Ga2O and NH3 gases flowing into an incised silica crucible. The Ga2O vapor was generated by carbothermal reduction of Ga2O3 at 970 degrees C. The effect of Ga2O generation rate (2-23 mu mol/min) on the morphology, crystallinity, cathodoluminescence property and impurity content was investigated. As the generation rate of Ga2O increased, the crystals changed from prismatic to needle-like shape, with a maximum prismatic crystal size of 1.7 mm x 0.3 min x 0.3 mm at the rate of 15 mu mol/min. The prismatic crystals were found to have high crystallinity by the narrow full-width at a half-maximum (40-70 arcsec) of their (10 (1) over bar0) X-ray rocking curves. Their good luminescence property was indicated by the intense cathodoluminescence peaks centered at similar to 3.47 eV. A relatively high concentration of oxygen (5 x 10(20) atoms/cm(3)) was contained in the crystals, as measured by secondary ion mass spectroscopy. (C) 2007 Elsevier B.V. All rights reserved.