Defect‐Polarization Coupling in 3D‐Graphene/ β ‐Ga ₂ O ₃ Heterostructures for Self‐Powered and Multifunctional Solar‐Blind Ultraviolet Photodetection

Solar‐blind ultraviolet photodetectors are promising for secure communication, early warning systems, and information security. Monoclinic phase gallium oxide ( β ‐Ga 2 O 3 ) is an ideal candidate due to its ultrawide bandgap. Unavoidable oxygen vacancies in β ‐Ga 2 O 3 have been viewed as detrimental defects that degrade performance. However, this study introduces an innovative approach that reinterprets these oxygen vacancies as beneficial for optoelectronic enhancement, accomplished through a 3D‐graphene/ β ‐Ga 2 O 3 heterojunction. Oxygen vacancies cause localized lattice symmetry breaking, generating dipole fields and local polarization. This interacts with the optical resonance of 3D‐graphene, enhancing optical and electrical fields in the heterojunction, which improves the separation and transport of photogenerated carriers. Experimental investigations, along with DFT and TCAD calculations, reveal that oxygen‐vacancy‐induced local polarization reduces the interfacial barrier, enhances electron injection, and increases photoconductive gain through a trap‐assisted mechanism. The photodetector achieves weak‐light detection at 255 nm (0.002 µW/mm 2 ) with a responsivity of 3740 A/W and specific detectivity of 6.85 × 10 13 Jones, a response of 140 µs, and enabling zero‐bias self‐powered operation. The 8 × 8 array allows for ultraviolet imaging and optical encrypted communication. This study reframes oxygen vacancies as functional mechanisms for enhancing polarization, paving the way for advanced wide‐bandgap optoelectronic device design.