GaN crystals growth in the Na-Li-Ca flux by liquid phase epitaxy (LPE) technique

•GaN crystal was grown by LPE technique in Na-Li-Ca flux solution at low temperature about 780 °C.•The smooth surface of as-grown GaN crystal was obtained because of lateral growth.•The dislocation density of as-grown GaN crystal could be directly reduced from 107 cm−2 to 103 cm−2.•The impurity defect concentration of as-grown GaN crystal could be decreased. 10 × 10 mm2 area GaN crystals were successfully grown on HVPE-GaN seed by LPE technique in Na-Li-Ca flux. Many growth hillocks with hexagonal shape were formed on the surface of crystal when the growth time was 150 h. Due to the lateral growth, the smooth Ga-face could be obtained after growth 300 h. The dislocation density could be decrease from 107 cm−2 to 103 cm−2 with increasing GaN crystal growth thickness. The reduction mechanism of dislocation was discussed. The PL spectra showed that the relative intensity of the yellow band luminescence peak of GaN crystals was obviously reduced comparing with HVPE-GaN seed, which indicated that the impurity defects in the crystal could be effectively suppressed.