Enhanced NO 2 Gas Sensing Performance of Multigate Pt/AlGaN/GaN High Electron Mobility Transistors

We report on Pt/AlGaN/GaN high electron mobility transistor (HEMT) based gas sensor with interdigitated electrodes for NO 2 sensing in the temperature range of 30 °C–300 °C. The effect of the length of platinum functionalization layer (gate length), gas detection limit and the activation energies were investigated in this work. It was found that the sensor with the shortest gate length exhibited the lowest sensing response, but highest responsivity and vice versa. The sensing response of 1.2% with the corresponding Δ I of 400 μ A was obtained for 50 ppb of NO 2 concentration, which is the lowest NO 2 concentration reported for Pt/AlGaN/GaN HEMT based sensors. Both the efficient sensing mechanism of the interdigitated electrodes and the catalytic property of platinum functionalization layer enable higher sensing response and lower detection limit for NO 2 . Activation energies of 0.33 eV/ion and 0.64 eV/ion for adsorption and desorption of O − ions, respectively have been determined in these sensors.