Fig. 1. (Color online) (a) XRDθ–2θ pattern of theβ-Ga₂O₃ thin films grown onc-plane sapphire substrates. The inset shows the XRD rocking curve of theβ-Ga₂O₃ ( 2¯01) reflection. (b) In-plane XRD Phi scans of for theβ-Ga₂O₃ film and sapphire substrate. (c) Cross-sectional HRTEM image of theβ-Ga₂O₃ film on sapphire. (d) XPS core-level spectra of O 1s and Ga 2p.

Fig. 2. (Color online) (a) SIMS depth profiles of the H-plasma treatedβ-Ga₂O₃ film on sapphire substrate. (b) Raman spectra of theβ-Ga₂O₃ film with and without H-plasma treatment. (c) XRDθ–2θ pattern of theβ-Ga₂O₃ thin films with and without the H-plasma treatment. (d) XRD rocking curve of theβ-Ga₂O₃ ( 2¯01) reflection for theβ-Ga₂O₃ film with and without the H-plasma treatment. (e) UV–vis absorption spectra of theβ-Ga₂O₃ film with and without H-plasma treatment. The Tauc plots of (αhν)² versushν is shown in the inset. (f) PL spectra of theβ-Ga₂O₃ film with and without H-plasma treatment. The H-plasma treatment was carried out with an RF power of 40 W and a H₂ flow rate of 50 sccm for 120 min.

Fig. 3. (Color online) Dependence of (a) the resistivity and (b) the Hall data of theβ-Ga₂O₃ films on the H-plasma exposure time. Dependence of (c) the resistivity and (d) the Hall data of theβ-Ga₂O₃ films on the RF power. Dependence of (e) the resistivity and (f) the Hall data of theβ-Ga₂O₃ films on the H₂ flow rate.

Fig. 4. (Color online) Temperature dependent (a) carrier concentration, (b) electron mobility, and (c) electrical resistivity for two typicalβ-Ga₂O₃ thin films after the H-plasma treatment. Dashed lines show the contributions to mobility from different scattering mechanisms, and the solid line shows the fitting total mobility.