Bias-Tunable Plasmonic Ga ₂ O ₃ /GaN Photodetectors for Reconfigurable Logic, Encryption, and Ultraviolet Imaging

Thermally oxidized Ga 2 O 3 /GaN heterojunctions offer a cost-effective route for ultraviolet (UV) detection. However, their application is often hindered by the high driving voltage required for effective near-UV (365 nm) response due to the transparency of the top wide-bandgap layer. Herein, a high-performance dual-band UV photodetector fabricated by decorating Ag nanoparticles (Ag NPs) onto an in situ thermally oxidized Ga 2 O 3 /GaN heterojunction is proposed. The Ag NPs, introduced via a solid-state dewetting process, induce a localized surface plasmon resonance (LSPR) effect that yields a dual-gain mechanism. Specifically, it enhances solar-blind (254 nm) responsivity through local field amplification and enables sensitive 365 nm detection at low bias via a hot-electron injection pathway. Leveraging this unique bias-tunable spectral response, reconfigurable optoelectronic logic gates (OR, NOR, and XNOR) are successfully constructed within a single device, overcoming the rigidity of traditional single-function logic units. Furthermore, a basic hardware-based optical encryption scheme based on XNOR logic and high-contrast single-pixel dual-color UV imaging are successfully realized. This work not only presents a strategy for low-power, high-performance UV detection but also paves the way for developing intelligent, secure, and in-sensor computing optoelectronic systems.