Fig. 1. (Color online) The simple diagram of the home-made vertical cylindrical dual temperature zone furnace.

Fig. 2. The growth rate of β-Ga₂O₃ films grown at different growth temperatures ranged from 1000 to 1350 °C.

Fig. 3. (Color online) Typical XRD θ–2θ scan of the β-Ga₂O₃ films grown on c-plane sapphire substrate at different temperatures of (a) 950 °C, (b) 1050 °C, (c) 1150 °C, (d) 1250 °C.

Fig. 4. The top view of SEM images of β-Ga₂O₃ film deposited at different growth temperatures. (a) Large area of film grown at 950 °C. Small area of film grown at (b) 950 °C, (c) 1050 °C, (d) 1350 °C.

Fig. 5. The growth rate of β-Ga₂O₃ films grown at different O₂ flow ranged from 5 to 100 sccm.

Fig. 6. (Color online) Typical XRD θ–2θ scan of the β-Ga₂O₃ films grown on c-plane sapphire substrate at different O₂ flow. (a) 50 sccm. (b) 20 sccm. (c) 10 sccm. (d) 5 sccm.

Fig. 7. The top view of SEM images of β-Ga₂O₃ film deposited at different O₂ flow. (a) 50 sccm. (b) 20 sccm. (c) 5 sccm.

Fig. 8. The growth rate of β-Ga₂O₃ films grown at different molar ratio between graphite and Ga₂O₃ powder.

Fig. 9. (Color online) Typical XRD θ–2θ scan of the β-Ga₂O₃ films grown on c-plane sapphire substrate at different molar ratio between graphite powder and Ga₂O₃ powder. (a) 20 : 1. (b) 10 : 1. (c) 5 : 1.

Fig. 10. The top view of SEM images of β-Ga₂O₃ film deposited at different molar ratio between graphite powder and Ga₂O₃ powder. (a) 20 : 1. (b) 10 : 1. (c) 5 : 1.