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

Large-size beta-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 beta-Ga2O3 crystals were discussed.