Enhancing Performance of Ultraviolet C Photodetectors Through Single-Domain Epitaxy of Monoclinic β-Ga 2 O 3 Films and Tailored Anti-Reflection Coating.

Implementing high-performance ultraviolet C photodetectors (UVC PDs) based on β-Ga 2 O 3 films is challenging owing to the anisotropic crystal symmetry between the epitaxial films and substrates. In this study, highly enhanced state-of-the-art photoelectrical performance is achieved using single-domain epitaxy of monoclinic β-Ga 2 O 3 films on a hexagonal sapphire substrate. Unlike 3D β-Ga 2 O 3 films with twin domains, 2D β-Ga 2 O 3 films exhibit a single domain with a smooth surface and low concentration of point defects, which enable efficient charge separation by suppressing boundary-induced recombination. Furthermore, a tailored anti-reflection coating (ARC) is adopted as a light-absorbing medium to improve charge generation. The tailored nanostructure, which features a gradient refractive index, not only substantially reduces the reflection, but also suppresses the surface leakage current as a passivation layer. This study provides fundamental insights into the single-domain epitaxy of β-Ga 2 O 3 films and the application of ARC for the development of high-performance UVC PDs.