GaN/Sn:Ga ₂ O ₃ @MgO/Graphene Core–Shell Nanowires for Self-Powered Deep-UV Photodetector

To address high dark current and surface defects in β-Ga 2 O 3 nanowire (NW) photodetectors, we report a multilayered core–shell heterostructure based on GaN/Sn:Ga 2 O 3 @MgO/graphene. Sn-doped Ga 2 O 3 NW arrays were grown via CVD on GaN substrates, followed by thermal evaporation of an MgO passivation shell and spin-coating of graphene. The MgO shell suppresses surface-state recombination and facilitates carrier separation through band bending, while the graphene layer optimizes carrier-transport paths and energy-level matching. Under 254 nm illumination (82 μW/cm 2 ), the device exhibits outstanding performance: a low dark current of 85.6 pA, a high PDCR of 2.13 × 10 4, a responsivity of 0.71 A/W, and a specific detectivity ( D *) of 2.40 × 10 13 Jones. This synergistic architecture provides a robust strategy for high-performance deep-ultraviolet (DUV) detection.