Growth of high-quality GaN crystals on a BCN nanosheet-coated substrate by hydride vapor phase epitaxy

In this study, boron carbon nitride (BCN) nanosheets were used as a substrate coating material to grow gallium nitride (GaN) crystals by hydride vapor phase epitaxy. By adjusting the solution viscosity, BCN nanosheets were uniformly coated on a MOCVD-GaN/Al2O3 substrate with spin-coating technology. Experiments with different conditions and the growth results showed that the BCN solution with a concentration of 0.0025 mg mL−1 and a viscosity of 14.30 mPa s was optimal for GaN growth. The quality of GaN crystals grown with BCN coating was significantly improved. The full width at half maximum (FWHM) values of the (002) and (102) planes were 192 and 213 arcsec, respectively, and the inside of the crystal was nearly unstressed. Compared with untreated or unevenly coated substrates, uniformly distributed BCN nanosheets effectively prevented the extension of threading dislocations, as well as promoted the lateral epitaxial growth of crystals and formation of small pores at the interface, which helped in relieving the stress inside the crystals and realizing the self-separating properties of GaN crystals. A GaN nucleation mechanism on the BCN nanosheets was discussed. EBSD and TEM results indicated that the crystal disorientation was reduced by using the BCN nanosheet-coated substrate. In general, the BCN nanosheets presented a broad application prospect in crystal growth.