In this work, we explore the possibility of using hybrid graphene/GaN phototransistors to get high responsivity, high speed, and large photosensitive area. The responsivity of our hybrid graphene/GaN phototransistors with a relatively large 15.2 mm² active area reaches 361 mA/W at 10 V and the response time is ~5 ms, much better performance than traditional GaN photodetectors. This is because graphene acts as the carrier transport channel with a high mobility and greatly increases the charge collection efficiency. Our results should shed more light on the role of graphene in hybrid phototransistors and open a feasible pathway to develop large area ultraviolet photodetectors with high responsivity and high speed.

Ultraviolet (UV) photodetectors with high responsivity and speed are highly desirable for imaging and remote sensing applications. Limited by the crystalline quality of a GaN-based material, which is ideal for UV photodetection, the further improvement of the performance is minimal. A hybrid graphene/unintentionally doped (UID) GaN UV photodetector with both high responsivity and high speed is reported. Holes in graphene, which are induced by the photogenerated electrons trapped at the graphene/UID GaN interface according to the capacitive effect, have a long lifetime owing to the electron-hole pair separation in space. Graphene acts as a carrier transport channel and greatly increases the charge collection efficiency under an external bias voltage. The responsivity of a hybrid graphene/UID GaN photodetector with a photosensitive area of 2 mm² reaches 5.83 A/W at −10 V with a specific detectivity of ∼10¹¹ Jones. The response time is ∼5 ms, which is faster than that of traditional GaN photodetectors. These results will provide a feasible route to UV detection with high performance.