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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. [ABSTRACT FROM AUTHOR]

High-quantity and large-size β-Ga2O3 single crystals were grown by the optimal edge-defined film-fed method. Under the excitation of 241Am α-ray, the scintillation light yields of the as-grown and after-annealed β-Ga2O3 single crystal are estimated to be 4797 and 6788 ph/5.5 MeV-α, respectively. The energy resolutions of the as-grown and after-annealed β-Ga2O3 single crystal are 21.8% and 19.1%, respectively. Annealing in the air can eliminate some color centers and decrease the concentration of free electrons, which can lead to the near-infrared absorption. The light yield and the energy resolution are some slightly worse than that of the commercial Bi4Ge3O12 (BGO) scintillator. However, the fast component with the time constant of 7 ns for the as-grown and after-annealed β-Ga2O3 single crystal reaches 25% of the total yield, suggesting that the β-Ga2O3 single crystal grown by the present method is a promising fast scintillator, which could be used in the ultrafast timing resolution detection systems. [ABSTRACT FROM AUTHOR]

We investigated the temperature-dependence of X-ray excited luminescence of β-Ga2O3 single crystals. The recombination of free-electrons with self-trapped holes (STHs) responsible for the ultraviolet luminescence (UVL) band was observed. For the as-grown sample with a high electron concentration, the Auger recombination becomes important, which accelerates the decay dynamics and reduces the ultraviolet luminescence band. The ultraviolet luminescence band is controlled by temperature quenching due to the migration of self-trapped holes to VGa3− centers. Annealing in an oxygen environment can increase the VGa3− concentration, which contributes to the blue-green luminescence band when VGa3− captures a self-trapped hole forming a VGa2− center at rising temperature. [ABSTRACT FROM AUTHOR]