Tunable Superlinear Gallium Oxide Gate-All-Around Deep-Ultraviolet Phototransistor for Near-Field Imaging.

Superlinear photodetectors hold significant potential in intelligent optical detection systems, such as near-field imaging. However, their current realization imposes stringent requirements on photosensitive materials, thereby limiting the flexibility of the device integration for practical applications. Herein, a tunable superlinear Ga2O3 deep-ultraviolet gate-all-around (GAA) phototransistor based on a p-n heterojunction has been proposed. Benefiting from the photogating effect, the device transitions from a cutoff to a saturated conducting state with increasing light intensity, exhibiting superlinear characteristics. This behavior can be electrically modulated via gate voltage, enabling flexible switching between linear and superlinear photoresponse. Additionally, it demonstrates an ultrafast response speed (749 μs), attributed to the junction-based GAA structure that accelerates the recombination of photogenerated carriers. Finally, the superlinear photoresponse of the Ga2O3 GAA transistor has been applied to near-field imaging, achieving nice focusing effects on images. Our research provides a feasible approach for the realization of superlinear photodetectors and their application in near-field sensing systems.