Stability of interfacial thermal balance in thick β-Ga2O3 crystal growth by EFG

•Higher temperature gradient near the upper surface of the die, from 17.40 K/mm to 27.46 K/mm.•Temperature gradients at different locations and the maximum pulling speed are calculated.•Growth interface instability due to heat accumulation occurs first in the center of the crystal then extends to the edges.•Two inch, 12mm thick Sn-doped β-Ga2O3 was obtained under 20mm/h pulling speed. When n-type β-Ga2O3 crystals with large thickness are grown by edge-defined film-fed growth (EFG), fusing often occurs, due to the massive release of latent heat of crystallization and infrared absorption of crystals, which affects the integrality and quality of crystals. In order to solve this problem, a furnace structure with larger axial temperature gradient (from 17.40 K/mm to 27.46 K/mm) over the die was designed by ANSYS FLUENT software. Considering the interface thermal and the pressure balance of the meniscus, the relationship between the overheating temperature on the upper surface of the die and the pulling speed was calculated. It is found that the overheated fusing starts from the center of the crystal and then to the edge, which is consistent with the actual growth of the crystal. The pulling speed of 20 mm/h was selected for the growth experiment. Through the optimization of thermal field environment and the selection of pulling speed, high-quality two-inch β-Ga2O3 crystals without overheat fusing was realized. This work provides more help for understanding β-Ga2O3 crystal growth by EFG.