Seeded growth of GaN by the basic ammonothermal method

Two preliminary experiments are reviewed and seeded growth of GaN is updated in this paper. In a mineralizer study, it was shown that basic mineralizers promoted synthesis of wurtzite GaN. Through a dissolution study of polycrystalline GaN in basic supercritical ammonia, it was confirmed that GaN has retrograde solubility. A GaN film as thick as 45 μm was obtained in seeded growth from metallic Ga nutrient. Uniform growth of GaN over a 3×4 cm2 oval-shaped seed crystal was also demonstrated. Seeded growth of GaN from polycrystalline GaN nutrient was attempted to avoid growth saturation problem in Ga nutrient. Extended growth up to 11 days was attained with increased mineralizer concentration. The cross-sectional TEM observation showed high density of voids and defects at the growth interface, although most of them did not propagate to the top surface. The estimated threading dislocation density was at the order of low–109 cm−2 and no evidence of basal plane stacking fault was observed.