Ammonothermal conversion of cyclotrigallazane to GaN:: Synthesis of nanocrystalline and cubic GaN from [H2GaNH2]3

Under ammonothermal conditions, cyclotrigallazane, [H2GaNH2](3), was converted to nanocrystalline GaN. The coherent length of the GaN product could be controlled by manipulating reaction time and temperature. Nanocrystalline GaN powders with average crystallite sizes of 3-17 nm were produced in the temperature range of 150-450 degrees C. Analysis of the powders by XRD and TEM indicated that the nanocrystals possessed a structure composed of a random arrangement of cubic and hexagonal close packed planes. The addition of NH4I to the reaction mixture resulted in the isolation of bulk samples of phase pure, cubic GaN at temperatures as low as 200 degrees C. The synthesis of the cubic phase was found to be temperature dependent, with mixtures of cubic and hexagonal GaN being produced at temperatures greater than 350 degrees C.