Research on the Simultaneous Growth of Four GaN Crystal Sheets by the Li-Added Na Flux Liquid Phase Epitaxy Method

The Na-flux liquid-phase epitaxial (LPE) method was employed to achieve the simultaneous growth of four GaN crystal sheets on HVPE-GaN seed. The effects of the amount of Li addition on the surface morphologies, thickness, yield, and quality of LPE-GaN crystals were researched. With the addition of 0.25 mol % Li, the growth thickness of samples #1–#4 shows a decreasing trend. The smooth epitaxial growth surface is formed by adding a small amount of Li to the Ga–Na melt. SIMS results show that the concentrations of both C and O in the transparent region are lower than those in the dark region. The XRC-fwhm values of the (0002) facet of samples #1–#4 with the addition of 0.25 mol % Li are 157, 146, 72, and 90 arcsec, respectively. The surface morphologies of LPE-GaN crystals for the same location (sample #3) exhibit pyramidal, smooth, smooth with holes, and polycrystalline structures for 0, 0.25, 0.35, and 0.50 mol % Li addition, respectively. The addition of Li enhances the solubility of nitrogen, and the thickness of GaN crystals exhibits a trend of initial increase followed by a subsequent decrease within the range of 0 to 0.50 mol % Li addition. XRC-fwhm values of the (0002) face of the four GaN crystals grown with 0.25 mol % Li addition were all lower than those of the corresponding positions of the crystals with other Li addition amounts. Therefore, by adding Li into the flux and further optimizing the growth parameters, it is promising to obtain high-transparency and high-quality GaN single crystals in the Na-flux LPE growth method.