AlGaN/GaN HEMT micro-sensor technology for gas sensing applications

Wide bandgap gallium nitride material has highly favorable electronic properties for next generation power and high frequency electronic devices. A less widely studied application is highly miniaturized chemical and gas sensors capable of operating in harsh environment conditions. In this work we present our recent developments on design, fabrication and testing of AlGaN/GaN high electron mobility transistor (HEMT) based sensors for detection of various gases. First, the method of as-fabricated device baseline value stabilization is demonstrated. Secondly, the impact of sensor design is discussed with the emphasis on gate electrode geometry optimizations to enhance sensing performance. Then we present the sensing characteristics of Pt-HEMTs towards H
2
S and compare them to H
2
and NO
2
. Finally we demonstrate recent results of NO
2
detection with Ti/Au based HEMT sensors, which are superior to those using Pt based devices.