Fig. 1. (Color online) Schematic diagram of Ga₂O₃ thin film deposition process.

Fig. 2. (Color online) (a) Growth rate of Ga₂O₃ films on Si as a function of O₂ plasma flow duration at 250 °C. (b) Growth rate and O/Ga ratio of Ga₂O₃ films on Si as a function of temperature. (c) The Ga₂O₃ thin films thickness as a function of the number of RPEALD cycles. (d) A comparison of Ga₂O₃ deposition rates on Si between this work and the reported literatures.

Fig. 3. (Color online) Growth rate of Ga₂O₃ thin films as a function of NH₃ plasma cycles.

Fig. 4. (Color online) High resolution XPS spectra of (a) Ga3d core level and (b) O1s core level, in Ga₂O₃ films. The insets in (a) and (b) show the overlap of Ga3d and O1s peaks from the Ga oxide films deposited by different processes.

Fig. 5. (Color online) AFM images of (a) Ga₂O₃ film deposited on Si without NH₃ plasma treatment, (b) Ga₂O₃ film deposited on GaN without NH₃ plasma treatment, (c) Ga₂O₃ film deposited on GaN with NH₃ plasma treatment, and (d) a comparison of roughness between this work and previous reported literatures.

Fig. 6. (Color online) SIMS depth profiles of (a) Ga₂O₃/Si and (b) Ga₂O₃/GaN. The insets in (b) show 3D images of SIMS data reconstructions of Ga₂O₃/GaN.

Fig. 7. (Color online) High resolution XPS spectra of (a) Ga3d core level and (b) O1s core level on GaN surface.

Fig. 8. (Color online) Ga3d core level spectra (a) w/o NH₃ plasma and (b) with NH₃ plasma, in Ga₂O₃ films.

Fig. 9. (Color online) the linear fitting of ln (1+R/R₀) against 1/sinθ.

Fig. 10. (Color online) High resolution XPS spectra of Ga3d core level (a) w/o NH₃ plasma and (b) with NH₃ plasma, in Ga₂O₃ film.

Fig. 11. (Color online) HRTEM analysis of Ga₂O₃ films on GaN deposited by RPEALD. (a) Cross-sectional TEM image of a Ga₂O₃/GaN structure without NH₃ plasma treatment. (a-1) Higher magnification views of the Ga₂O₃/GaN interface without NH₃ plasma treatment. (a-2) FFT of Ga₂O₃ films deposited on GaN without NH₃ plasma treatment. (b) Cross-sectional TEM image of a Ga₂O₃/GaN structure with NH₃ plasma treatment. (b-1) Higher magnification views of the Ga₂O₃/GaN interface with NH₃ plasma treatment. (b-2) FFT of Ga₂O₃ film deposited on GaN with NH₃ plasma treatment.

Table 1. Deposition recipe for Ga₂O₃ thin films.