IoT-Enabled hBN/AlGaN/GaN High Electron Mobility Transistor for Carbon Dioxide Monitoring

Monitoring carbon dioxide (CO2) is critically prudent across various domains such as environmental surveillance, industrial processes, and space applications due to its considerable impact on climate change and human wellbeing. Conventional CO2 sensors often have limitations of high response time, poor resolution, large size, and short operational lifetime. This work presents a CO2 sensor to address the challenges, exploiting an AlGaN/GaN High Electron Mobility Transistor (HEMT) functionalised with hexagonal boron nitride (hBN). This sensor leverages the high electron mobility of the two-dimensional electron gas (2DEG) at the AlGaN/GaN interface and the selective adsorption properties of hBN. Characterisation results show the highest selectivity and sensitivity towards CO2, with a tested detection range from 1 ppm to 100 ppm, a response of 56°/0 at 100 ppm, and a response time of about 120 seconds. The sensor was also integrated with an ESP32 IoT module for real-time monitoring and data transmission. The operational principle involves CO2 adsorption on the hBN layer, leading to changes in the 2DEG conductivity and measurable variations in the sensor's electrical characteristics. The results underscore the potential of AlGaN/GaN HEMT-based sensors in environmental monitoring and industrial applications.