Transport growth of GaN crystals by the ammonothermal technique using various nutrients

The nutrient transport direction for the growth of GaN crystals in ammonobasic solutions was investigated. Growth of GaN crystals via nutrient transport from the cold zone to the hot zone in alkaline solutions by the ammonothermal technique was confirmed using three kinds of nutrients: gallium metal, gallium-containing intermediates and polycrystalline GaN. Ga-containing intermediates are easily formed when using gallium metal or GaN as nutrient, and remain stable at temperatures below 400 °C; GaN is deposited in the hot zone of the autoclave only at high temperatures greater than 500 °C. Transport growth of GaN crystals from polycrystalline GaN nutrient in the cold zone to hydride vapor phase epitaxy (HVPE) seeds in the hot zone in alkali supercritical ammonia was also achieved. The study has clearly demonstrated that gallium-containing intermediates are the stable phases at lower temperatures, and that GaN bulk crystals (substrates) can be grown in the hot zone at high temperatures from ammonobasic solutions by the ammonothermal technique.