Effect of temperature on CO sensing response in air ambient by using ZnO nanorod-gated AlGaN/GaN high electron mobility transistors

AlGaN/GaN high electron mobility transistors (HEMTs) functionalized with ZnO nanorods were used for sensing CO in the concentration range of 50-500 ppm balanced with air at ambient and temperatures from 25 to 250 °C. An increase of the HEMT drain current was observed for exposure to the CO-containing ambient. The sensing limitation was improved from 100 ppm to 50 ppm by increasing the sensor temperature from room temperature to 250 °C. The sensing response was also enhanced from 0.09% to 0.34% by increasing the sensor temperature. Reliable and repeatable current changes with the introduction of a low CO concentration of 50 ppm and also rapid response times of ∼40 s and recovery times ∼15 s were demonstrated.