High Performance NO₂ Gas Sensor Based on Pd-AlGaN/GaN High Electron Mobility Transistors with Thin AlGaN Barrier

We investigated the performance of NO₂ gas sensors based on AlGaN/GaN high electron mobility transistors (HEMT) with 10 nm AlGaN barrier. The sensors were designed to operate in μA range to reduce power consumption and realize good sensing performance. The gate area of the HEMT sensor was functionalized using a Pd and Pt catalyst layer for NO₂ detection to compare the performance between Pd and Pt catalysts. Pd-functionalized sensors demonstrated better sensing characteristics compared with Pt-functionalized sensors. When the sensors were exposed to 100 ppm of NO₂ at 300℃, the relative sensitivity of 53 % was measured with the response time and recovery time of 136 s and 196 s, respectively. Also, the sensor shows a significant change of drain current for 30 s exposure time in different concentrations from 10 to 100 ppm NO₂. These results suggest that Pd-AlGaN/GaN HEMT sensors with a thin barrier can be the great choice to detect NO₂ gas and they could be used in the harsh environment in real-time condition.