We report improved sensitivity to NO, NO2 and NH3 gas with specially-designed AlGaN/GaN high electron mobility transistors (HEMT) that are suitable for operation in the harsh environment of diesel exhaust systems. The gate of the HEMT device is functionalized using a Pt catalyst for gas detection. We found that the performance of the sensors is enhanced at a temperature of 600 °C, and the measured sensitivity to 900 ppm-NO, 900 ppm-NO2 and 15 ppm-NH3 is 24%, 38.5% and 33%, respectively, at 600 °C. We also report dynamic response times as fast as 1 s for these three gases. Together, these results indicate that HEMT sensors could be used in a harsh environment with the ability to control an anti-pollution system in real time.

G ALLIUM nitride-based chemical sensors have attracted much interest for sensing applications. Gallium nitride devices operate stably at high temperatures and can resist chemical corrosion. GaN-based sensors have even been demonstrated to function in the presence of Cl 2 gas and HCl vapor [1]. Because of these favorable properties, GaN-based sensors are attractive for automotive exhaust applications C. Bishop, P. L. Voss, and A. Ougazzaden are with the School of Electrical and Computer Engineering,