New Flux-Excess Aid Technology in the Na-Flux Liquid-Phase Epitaxial Growth of GaN Crystals

2 in. GaN crystals (2 in.) were grown on MOCVD-GaN films by the Na flux liquid-phase epitaxial (LPE) method with a new flux-excess aid technology. By adding a certain amount of additional Na flux during the growth process, the height of the growth solution remained essentially unchanged after growth, meaning that Na volatilization was effectively suppressed. The effects of flux-excess on GaN crystal growth were investigated. The results show that the grown GaN crystal has a flatter crystal surface, an epitaxial thickness of up to ∼1500 μm, and the single-crystal yield has a 19% increase compared to nonflux-excess condition. X-ray rocking curves results on the surface of the crystal (0002) show that the fwhm of the flux-excess grown crystal is about 344 arcsec, a marked improvement over the nonexcessive condition (∼1488 arcsec). Simulations of the distribution of the nitrogen concentration in the Ga–Na melt at the beginning and end of the growth revealed that the nitrogen concentration is higher for flux-excess growth than that for nonexcessive growth, and that the nitrogen concentration is lower in the center near the surface of the seed crystals and higher at the edges. Therefore, the flux-excess aid technology may provide a pathway to realize the growth of high-quality GaN crystals using the Na-flux LPE growth method.