Dual-Gas Sensor Based on the Pt NPs/AlGaN/GaN High Electron Mobility Transistor for H and NH Gases Detection

Multisensitive gas sensors have been drawing increasing attention in recent years. In this work, dual-gas detection of hydrogen (H2) and ammonia (NH3) is demonstrated based on the Pt NPs/AlGaN/GaN high electron mobility transistor (HEMT) device by solely tuning the operating temperature. Scanning electron microscopy (SEM) and atomic force microscope (AFM) results show that the 3 nm-thick Pt layer is a porous film with roughness of 1.2 nm. According to the
${I} _{\text {d}}-{V} _{\text {g}}$
curves, the device has a pronounced pinch-off characteristic with an on-to-off ratio of five orders of magnitude. Interestingly, this device is a H2 gas sensor below 150 °C and it changes to NH3 gas sensor above 180 °C. Our sensor has a high response of 280.4% at 200 ppm NH3 gas and an ultrafast response time of 4 s at 220 °C. Experimentally, the device has a clear response of 1.9% at 100 ppb, indicating very low limit of detection (LOD). The capability of dual-gas detection makes it attractive for multigas detection and electronic nose.