Low Hg(II) ion concentration electrical detection with AlGaN/GaN high electron mobility transistors

Thioglycolic acid functionalized Au-gated AlGaN/GaN high electron mobility transistors (HEMTs) were used to detect mercury(II) ions. The drain current of the HEMT sensors monotonically increased with the mercury(II) ion concentration from 1.5 × 10−8 to 4 × 10−8 M. The drain current reached equilibrium around 15–20 s after the concentrated Hg ion solution added to the gate area of the HEMT sensors. The effectiveness of the thioglycolic acid functionalization was evaluated with a surface contact angle study. The results suggest that portable, fast response, and wireless-based heavy metal ion detectors can be realized with AlGaN/GaN HEMT-based sensors.