Vapor-phase growth of high-quality GaN single crystals in crucible by carbothermal reduction and nitridation of Ga2O3

Highly crystalline gallium nitride (GaN) single crystals with good luminescence property were grown at 1200 °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 °C. The effect of Ga2O generation rate (2–23 μmol/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×0.3 mm×0.3 mm at the rate of 15 μmol/min. The prismatic crystals were found to have high crystallinity by the narrow full-width at a half-maximum (40–70 arcsec) of their (1 0 1¯ 0) X-ray rocking curves. Their good luminescence property was indicated by the intense cathodoluminescence peaks centered at ∼3.47 eV. A relatively high concentration of oxygen (5×1020 atoms/cm3) was contained in the crystals, as measured by secondary ion mass spectroscopy.