Improving the purity of GaN grown by the ammonothermal method with in-autoclave gas-phase acidic mineralizer synthesis

In-autoclave synthesis of a gas-phase acidic mineralizer was investigated for high-purity GaN growth by the ammonothermal (AT) method. To reduce oxygen contamination of GaN from highly hygroscopic NH ₄Cl powder, purified NH ₃ and HCl gases were introduced sequentially fed into a Pt-lined autoclave to synthesize NH ₄Cl within the autoclave. The autoclave was pre-charged with GaN seed wafers and polycrystalline precursors, and carefully dehydrated under dynamic vacuum. Because of the decrease in oxygen concentration, the lattice parameter approached the intrinsic value. The Ga-polar layers exhibit a near-band-edge emission peak at room temperature.