High-pressure high-temperature synthesis of GaN with melamine as the nitrogen source

Micron-sized grains of gallium nitride (GaN) crystallizing in the Wurtzite phase were synthesized through a chemical reaction between gallium (Ga) metal and melamine (C3N6H6). The reaction occurred at the temperature range from 1073 to 1473 K and the pressure range from 3.5 to 5.5 GPa. X-ray diffraction (XRD) and transmission electron microscopy (TEM) investigations showed that the final black products mainly contained the clusters of tiny GaN crystals. Prism-like well-shaped single crystals were found in the TEM micrographs. A vapor–liquid–solid growth process was proposed to explain the growth mechanism of GaN in which the pyrolysis of melamine was responsible for the provision of reactive nitrogen.