Powder synthesis and ammonothermal crystal growth of GaN from metallic Ga in the presence of NH4I

An efficient and mild method to synthesize high-purity hexagonal GaN powder using NH4I as a catalyst was developed. The method makes it possible to use Ga metal for ammonothermal crystal growth of GaN at a rate of 20 μm per day, which is comparable to its growth rate using polycrystalline GaN grown by hydride vapor phase epitaxy as a nutrient.