Impact of the sensor temperature on low acetone concentration detection using AlGaN/GaN HEMTs

Abstract

In this work, we report on AlGaN/GaN HEMT sensors for acetone concentration below 100ppm and in a broad range of the sensor temperature varying from RT to 300 ∘C. At RT, in the presence of acetone, a smooth and monotonic decrease of the current is observed with a rather large response of 15A/ppm and with a large response time (several minutes) and memory effect. At a high temperature (300 ∘C), a current decrease is first observed just after the acetone injection, then followed by an increase, which saturates and stabilizes at a constant value. In order to clarify this unexpected behaviour, a detailed study of the sensor response versus the temperature and acetone injection flow is carried out. The outcome of this investigation is that a competition between the current variations induced by both the sensor and gas flow temperature difference from one side and the acetone dipolar moment from the other side can explain this transient. Our study highlights that AlGaN/GaN HEMT-based sensors allow for very sensitive acetone detection at both room and high temperatures. Nevertheless, care must be taken during the characterization and operation of such sensors especially at high operating temperatures. On the other hand, the high temperature operation helps to improve the sensor response and suppress the memory effect.