p-Type β-Ga2O3 film room-temperature NH3 gas sensors with fast gas sensing and a low limit of detection†

Ammonia (NH₃) gas sensing is critical for practical applications in the environmental monitoring of NH₃ pollution from food, chemical and agricultural industries. However, it is difficult to achieve room-temperature (RT) ammonia gas sensors fabricated on n-type Ga₂O₃ materials owing to the weak exchange of carriers between NH₃ gas and surface-adsorbed oxygen ion species for n-type semiconductors. Good sensing performance is expected to be achieved by p-type Ga₂O₃ gas sensors because of the special gas adsorption and chemisorbed reactions of the surface hole-accumulation layer. In this study, p-type N-doped β-Ga₂O₃ film gas sensors with RT NH₃ gas sensing were fabricated with wide hole-accumulation layers of 44.5 nm at 300 K. The p-type β-Ga₂O₃ gas sensors exhibited a response of 219.1% and short response/recovery time of 42.3/60 s towards 50 ppm NH₃. The good response linearity with a linearity factor of 0.33 and a low limit of detection of 1 ppm were observed for the p-type β-Ga₂O₃ gas sensors. The good RT NH₃ sensing performance originates from the wide hole-accumulation layer with the good gas adsorption and chemisorption reactions. This work opens an avenue for the fabrication of RT NH₃ gas sensors on p-type oxide films, lays the foundation for p-type β-Ga₂O₃ gas sensing, and paves the way for the evolution of RT gas sensors fabricated on p-type oxides.