【Epitaxy Papers】Bilayer architecture for high-quality β-Ga₂O₃ thin films on Si

      Researchers from Shanghai University、Peking University and Nantong University have published a dissertation titled " Bilayer architecture for high-quality β-Ga₂O₃ thin films on Si " in Journal of Crystal Growth.

Abstract

      The growth of high-quality Ga₂O₃ thin films on silicon (Si) substrates using radio frequency (RF) magnetron sputtering has emerged as a critical research focus for fabrication of high-performance photoelectric devices. Previous studies have extensively documented the influence of sputtering parameters and post-annealing techniques on film characteristics. This report reveals that post annealing at 1000 °C not only induced α-to-β phase transition for single-layer Ga₂O₃ thin films, but also effectively increased crystallite and reduced microstrain in the films. However, thermal treatment counterintuitively increased the oxygen-vacancy (V_O) concentration from 27.5% to 32.0%, as quantified by XPS analysis. The surface-adsorbed oxygen component in the XPS spectra completely disappeared after annealing, indicating film densification. The increase in the near-surface V_O ratio may result from an imbalance between oxygen incorporation from the annealing atmosphere and thermally induced oxygen redistribution toward the Ga₂O₃/Si interface. To overcome this detrimental annealing effect, a bilayer architecture consisting of an oxygen-deficient Ga₂O₃ bottom layer and an active Ga₂O₃ top layer was proposed. Remarkably, under the same annealing conditions, the bilayer film exhibited a decrease in V_O concentration from 31.6% to 25.3%, a complete reversal of the trend. The oxygen-deficient layer was associated with reduced interfacial stress and modified oxygen-exchange kinetics during annealing, while cross-sectional EDS elemental mapping showed a less pronounced extension of the O signal toward Si in the bilayer film than in the single-layer film. Consequently, the bilayer film showed larger crystallites, lower microstrain, smoother surface morphology, and suppressed blue–green defect-related photoluminescence. This work demonstrates that a rational bilayer design can transform a deleterious annealing effect into a beneficial one, providing a practical route to high-quality β-Ga₂O₃ thin films on Si.

DOI：

https://doi.org/10.1016/j.jcrysgro.2026.128838