Interaction activated interfacial charge transfer in 2D g-C3N4/GaN nanorods heterostructure for self-powered UV photodetector and room temperature NO2 gas sensor at ppb level

In this work, we demonstrated a single device of g-C3N4/GaN NRs heterostructure with dual functionality for self-powered ultraviolet light photodetector and selective NO2 gas sensor at room temperature. The g-C3N4/GaN NRs heterostructure demonstrated excellent photoresponse to UV illumination (λ = 392 nm) at zero bias with linear dependence on illumination power. Under 1.35 mW/cm−1 illumination power, the device exhibited high responsivity∼20 mA/W, and detectivity ∼5.16 × 1012 cmHz1/2/W. On the other hand, the g-C3N4/GaN NRs heterostructure exhibited remarkable response of 7.8 % for 5 ppm NO2 gas, while pristine GaN NRs showed negligible response. The potentiality of the gas sensor is further boosted by irritation of UV and visible lights, and the limit of the detection enriched to 500 ppb under UV illuminations at RT. UV light (P = 1.35 mW/cm2) greatly intensified the response by five-fold, and notably stimulated the recovery signal of the device for 500 ppb NO2. The increased response of heterostructure is ascribed to the sensitization of g-C3N4 and the adequate interface between g-C3N4 and GaN NRs that promoted the charge transport and separation effectively. The photodetector and NO2 gas sensing mechanism of g-C3N4/GaN NRs junction is discussed in detail by using energy band diagram.