GaN crystals were grown at 1200℃ by vapor phase reaction of NH_3 and Ga_2O, produced by carbothermal reduction of Ga_2O_3 powder. In 2h growth, the slow Ga_2O flow rate (7-14 μmol/min^<-1>) gave millimeter-sized hexagonal prism wurtzite-type GaN crystals, while the high rate (21 μmol/min^<-1>) formed the needle crystals.
