Low concentration hydrogen detection properties of metal-insulator-semiconductor AlGaN/GaN HEMT sensor

Abstract

In this paper, a Pt/Al2O3/AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT) sensor was fabricated for sensing hydrogen (H2) gas and compared to a more conventional Pt-HEMT sensor. The drain-source current (Ids) versus gate-source voltage (Vgs) property (transfer curve) and hydrogen detection characteristics in synthetic air ambient between the HEMT sensor and MIS-HEMT sensor were investigated and compared. It was observed that the MIS-HEMT sensor had a relatively higher resolution in the 100–3000 ppm range than the resolution from 10 to 100 ppm, and a better sensing response for 10 ppm of H2 at 200 ℃ and 225 ℃ using the first-derivative method, which is based on the drain current derivative with respect to time (dIds/dt). When using the real-time method, which is based on the Ids versus time, the measured sensing signal response (recovery) times of the MIS-HEMT with the Al2O3 gate insulator layer reduced to 36 (120) s in comparison to the HEMT sensor values of 44 (175) s. In terms of the dIds/dt method, the response (recovery) time was improved from 4 (2) s to 2 (2) s by using the MIS-HEMT structure.