Self-Powered Ultraviolet-C Imaging Using Epitaxial Gallium Oxide Membranes with Anisotropic Domain Conduction

High efficiency of charge carrier conduction is crucial for photoelectrical performance in ultraviolet C (UVC) photodetectors (PDs) based on heteroepitaxial beta-gallium oxide (β-Ga₂O₃) thin films. However, the presence of in-plane rotational domains due to anisotropic symmetry severely degraded the efficiency of charge carrier conduction by trapping and recombination of carriers in conventional lateral PD (LPD). Here, we demonstrate an approach that enables vertical conduction configuration while preserving the high crystallinity of epitaxial Si-doped β-Ga₂O₃ (Si:Ga₂O₃) through the epilayer transfer using a hole pattern sapphire nanomembrane (HPSN) growth template. Based on the characterization of domain orientation and photoresponsivity in transferred epitaxial Si:Ga₂O₃ membranes, we reveal the defect-related anisotropic conduction arising from the vertical interdomain and lateral intradomain conduction. Compared to the indirect intradomain pathway in LPD, the vertical PD (VPD) exhibited high efficiency of charge carrier conduction through the direct interdomain pathways. As a result, the self-powered VPD exhibits high rectifying characteristics with a high detectivity of 1.02 × 10¹³ Jones and a fast response time of 93 ms. Moreover, the multipixel UVC imaging PD arrays have been successfully demonstrated without any external applied bias, showing high recognition rates and practical utility for reliable UVC imaging applications. Our work not only demonstrates the feasibility of obtaining single-crystal epitaxial membranes for a wide range of material systems but also provides pathways for overcoming material limitations with defect-induced optoelectrical systems.