Dislocation evolution along the growth direction of 2-inch GaN crystal grown by Na-flux LPE

2-inch GaN crystals with 1170 μm thickness were successfully grown on MOCVD-GaN thin film seed by Na flux liquid phase epitaxy (Na-flux LPE) technique. X-ray diffraction analysis confirmed that the structure of as-grown GaN crystals was wurtzite. The dislocation etching pit morphologies of GaN crystals at different growth thicknesses were observed by SEM using chemical etching and the dislocation densities were measured. The dislocation density decreased as the growth thickness increased, which could decrease to 105 cm−2 order at the thickness of 870 μm, comparing to about 108 cm−2 of original MOCVD-GaN thin film seed. The mechanism of dislocation density reduction was discussed.