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 beta-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 beta-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 beta-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 beta-Ga2O3 gas sensing, and paves the way for the evolution of RT gas sensors fabricated on p-type oxides.