Fig. 1. (Color online) (a) RHEED patterns before and after the deposition of β-Ga₂O₃ films. (b) XRD in-plane ϕ scan for the β-Ga₂O₃ film grown at substrate temperature of 630 °C.

Fig. 2. (Color online) (a) XRD 2θ–ω scan of Ga₂O₃/ Al₂O₃ grown at 630 °C. (b) Surface morphology investigated by AFM in a scanned area of 3 × 3 μm².

Fig. 3. (Color online) A growth diagram for the Ga₂O₃ MBE growth. The Ga flux dependent growth rate of Ga₂O₃ grown at different temperatures.

Fig. 4. (Color online) (a) XRD patterns of Ga₂O₃ films deposited on (0001) sapphire substrates with different substrate temperatures. (b) The growth temperature dependent FWHM of XRD ω-scan for ( ) plane of Ga₂O₃ films.

Fig. 5. (Color online) AFM surface morphology of β-Ga₂O₃ deposited at different substrate temperatures. (a) 630 °C. (b) 680 °C. (c) 730 °C. (d) 780 °C.

Fig. 6. (Color online) RT-CL spectra of (a) 400-nm-thick β-Ga₂O₃ film, (b) cross sectional β-Ga₂O₃ thin film, (c) Al₂O₃ substrate.