【Epitaxy Papers】A comparative study on heteroepitaxial β-Ga₂O₃ on off-cut C-plane sapphire towards: M-plane vs. A-plane

      Researchers from Beijing Institute of Technology have published a dissertation titled " A comparative study on heteroepitaxial β-Ga₂O₃ on off-cut C-plane sapphire towards: M-plane vs. A-plane" in Journal of Physics D: Applied Physics.

Abstract

      Off-cut c-plane sapphires towards a-plane (C-A) and m-plane (C-M) with various angles have been studied for the heteroepitaxial growth of beta gallium oxide (β-Ga₂O₃) films. The β-Ga₂O₃ films grown on C-A and C-M substrates exhibit enhanced crystallinity as the off-angle increases from 0° to 6°, which is ascribed to the constrained sixfold epitaxial growth orientations. The C-M samples exhibit narrower XRC peaks than the C-A samples, however, the underlying mechanism remains unclear. It is find that the β-Ga₂O₃ film grown on a-axis 6° off-cut exhibits two epitaxial orientation peaks separated by 120°, while those on m-axis 6° off-cut are separated by 60°. Moreover, the mirror symmetry of oxygen arrangements exists along the a-axis, which is broken along the m-axis to exhibit structural irregularity. The breaking of oxygen symmetry along the m-axis effectively reduces the regularity of the off-cut steps during epitaxial growth, thereby aligning the growth directions and improving crystal quality. Interestingly, although the film crystallinity of C-A sample is improved by raising the offcut angle to 8°, an additional (-604) plane is observed to suggest the emergence of an additional crystallographic orientation. These findings provide critical insights for designing offcut directions to improve the quality of β-Ga₂O₃ on sapphire and other heterogeneous epitaxial films.

DOI：

https://doi.org/10.1088/1361-6463/aea6ea