Inhibition of volatilization and polycrystalline cracking, and the optical properties of β-Ga₂O₃ grown by the EFG method

Large-size β-Ga₂O₃ single crystals without sub-grain boundaries and cracks were grown by the optimized EFG technology. The thermal volatilization of Ga₂O₃, polycrystalline growth and cracking were systematically characterized and analyzed from phenomenological and crystallographic points. The proportion of CO₂ gas in the growth atmosphere and axial temperature gradient of the thermal field play important roles in suppressing the thermal decomposition and volatilization of a Ga₂O₃ melt. A higher seeding temperature could effectively inhibit polycrystalline growth. Furthermore, the effects of annealing in an oxygen environment on the optical properties of β-Ga₂O₃ crystals were discussed.