TiO2 Functionalized AlGaN/GaN HEMT Gas Sensor Based on Capacitance Change Strategy under Room Temperature

A fast response and high-selectivity TiO2@Polymine (PEI) modified AlGaN/GaN high electron mobility transistor (HEMT) gas sensor is proposed and fabricated. It can be used to detect formaldehyde (HCHO) under room temperature (RT, about 25 degrees C). The working mechanism of this sensor is to affect the channel current by changing the cap capacitance of HEMT. The capacitance of amino-functionalized TiO2 as photocatalyst changes with the adsorb and degrade process under UV irradiation (365 nm, 2 mW). Compared with volatile organic compounds (VOCs), it has exhibited excellent gas-sensing performance for HCHO vapour. The detection limit of HCHO is 5 ppm and the signal sensitivity is 312 nA/ppm at RT. Due to the low operating voltage and small sensor size, it is expected to be simple and portable.