Highly conductive Si-doped β-(AlxGa1−x)2O3(010) thin films via mist chemical vapor deposition

Recently, β-Ga2O3 has garnered the attention of researchers for power switching applications owing to its high breakdown field. β-(AlxGa1−x)2O3 (AlGaO), formed by alloying Ga2O3 with Al2O3, is also expected to enable rapid switching applications by forming a two-dimensional electron gas layer at the β-AlGaO/Ga2O3 interface. In this study, we demonstrated the epitaxial growth of Si-doped β-AlGaO thin films using the mist chemical vapor deposition technique to achieve high conductivity in β-AlGaO thin films. We achieved high crystallinity with Laue fringes observed in the x-ray diffraction 2θ–ω peaks of 020 Si-doped β-AlGaO thin films, and coherent growth was confirmed via reciprocal space mapping. Atomic force microscopy images revealed smooth surfaces with small root mean square (RMS) roughness values below 1 nm, although the RMS roughness increased with higher Si doping and Al composition. SIMS measurement revealed a Si concentration of ∼1 × 1019 cm−3, and unintentional impurities, such as C and H, which can act as donors, were incorporated in the β-AlGaO thin film with a carrier concentration of 1.5 × 1019 cm−3. Regarding Fe, some diffusion from the Fe-doped substrate to the thin film was observed at concentrations less than 1018 cm−3. Furthermore, room-temperature Hall effect measurements showed the influence of Al composition on carrier concentration. The thin film exhibited the highest conductivity of 971 S/cm, with a carrier concentration of 6.21 × 1020 cm−3 and Hall mobility of 9.8 cm2/Vs. Furthermore, we performed temperature-dependent Hall effect measurements to analyze the scattering properties of degenerate β-AlGaO. These findings contribute to the advancement of β-Ga2O3-based device applications.