Detection of heavy metal ions using meander gated GaN HEMT sensor

Abstract

We have developed a fast and simplistic AlGaN/GaN high electron mobility transistor (HEMT) for the detection of heavy metals such as mercury, lead, copper and zinc in water with a dynamic range of 1 nM to 1 mM. Four device designs have been fabricated where the gate structure and the distance between the source and the drain have been varied. It is observed that the device with meander gated (MG) structure and larger sensing area showed better response. A detailed analysis of the surface of the samples has been also investigated using SEM, EDS and Raman spectroscopy which confirms the re-usability of the sensor for a longer period of time. The response of the sensor stabilizes at 35 and 27 s for mercury and copper ions respectively. The response time of the sensor also shows a concentration dependent behavior. The sensor exhibits the high sensitivities of 31, 38, 35, and 24 mV/decade [M] for mercury, copper, zinc and lead ions respectively.