Abstract
Ammonothermal growth of GaN was studied through three types of experiments: synthesis of powder GaN from metallic Ga with various kinds of mineralizers, a weight loss measurement of polycrystalline GaN, and growth of GaN via fluid transport. Hexagonal (wurtzite) GaN was exclusively synthesized with basic mineralizers, whereas neutral and acidic mineralizers resulted in a mixture of hexagonal and cubic (zinc blende) phases, confirming that basic mineralizers are suitable for growing hexagonal GaN. Through a dissolution study of GaN in basic supercritical ammonia, it was discovered that the solubility of GaN has negative temperature dependence. Based on these results, the Ga nutrient was placed in a lower temperature zone and GaN was precipitated on single crystalline GaN seeds. Seeds placed in a higher-temperature zone showed more weight gain than those in a lower-temperature zone. Spontaneously nucleated precipitates on the GaN seeds showed clear crystallographic facets. The maximum size obtained in 24-h growth was about 10 μ m. Deposition of planar GaN on seed surfaces was also confirmed.
Published Version
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