Enhancing Performance of Ultraviolet C Photodetectors Through Single‐Domain Epitaxy of Monoclinic β‐Ga2O3 Films and Tailored Anti‐Reflection Coating

Implementing high‐performance ultraviolet C photodetectors (UVC PDs) based on β‐Ga2O3 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‐Ga2O3 films on a hexagonal sapphire substrate. Unlike 3D β‐Ga2O3 films with twin domains, 2D β‐Ga2O3 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‐Ga2O3 films and the application of ARC for the development of high‐performance UVC PDs. Single‐domain β‐Ga2O3 epitaxial films on sapphire substrates suppress boundary‐induced recombination while having a low concentration of point defects and show efficient photogenerated charge separation. Tailored anti‐reflection coating (ARC) with a forming gradient refractive index (n) not only substantially improves charge generation, but also suppresses dark current (Idark) as passivation layers exhibiting a high‐performance ultraviolet C photodetector.