Ammonothermal growth of GaN on a self-nucleated GaN seed crystal

We performed ammonothermal synthesis of a self-nucleated GaN seed and grew crystalline GaN on the seed in the presence of an NH₄F-based mineralizer. Our results suggest that spontaneously nucleated, high-quality GaN crystals can be obtained by recrystallization of polycrystalline hydride vapor phase epitaxy (HVPE) GaN under acidic ammonothermal conditions. We achieved average growth speeds of up to 410 and 465 μm/day on the c- and m-directions, respectively, after four consecutive crystal growths of GaN on a self-nucleated seed. GaN crystals grown on an HVPE seed and on a self-nucleated seed had comparable crystal quality, judged from room-temperature photoluminescence measurements.