Ag-modified GaN thin films via thermal diffusion and etching: A new frontier in high-sensitivity NO2 gas sensors

Gallium nitride (GaN)-based gas sensors are widely recognized for their excellent carrier mobility, high-temperature resistance, and corrosion resistance, making them suitable for extreme working conditions. However, pure-phase GaN suffers from poor sensitivity and slow response/recovery rates due to its surface chemical stability. In this work, we proposed an Ag-modified GaN thin film, fabricated via magnetron sputtering, for direct integration into a sensor device for room-temperature NO 2 detection. The Ag modification is achieved through a dual approach: thermal diffusion combined with sputtering, followed by wet etching. The optimized Ag-GaN sensor demonstrates a maximum response of ∼4.3 toward 10 ppm NO 2 at room temperature (25 ± 3 °C), with excellent linearity across two concentrations range (1–10 ppm and 400–1000 ppb). The device exhibits a theoretical detection limit of ∼1.35 ppb and a response/recovery time of 150/400 s. Furthermore, the sensor shows highly reversible reaction-recovery behavior, with 2.05 % relative standard deviation (RSD), indicating outstanding repeatability. These findings advance the application of GaN-based materials in gas sensing, particularly for sensitive and reliable NO 2 detection at room temperature.