Detection of cadmium ions Byg-C₃N₄ functionalization on AlGaN/ GaN high electron mobility transistor

In this study, a novel, highly sensitive AlGaN/ GaN high electron mobility transistor (HEMT) sensor is demonstrated for the detection of cadmium ions by the functionalization of graphitic carbon nitride (g-C₃N₄). The preparation of g-C₃N₄ was done using the pyrolysis process of urea. The prepared g-C₃N₄ was functionalized on Au gated AlGaN/ GaN HEMT and the sensing performance was observed by the measurement of electrical characteristics of the device. The sensitivity and limit of detection of the modified g-C₃N₄ based AlGaN/ GaN HEMT sensor was observed as 0.2606 µA/ppb and 0.533 ppb respectively. The observed limit of detection is very low than the standard guideline values of World Health Organization (WHO) for drinking water. Furthermore, using AlGaN/GaN HEMT theory, we show that the sensing response is very fast due to the availability of 2-D electron gas (2DEG) and very sensitive due to the change in gate potential. The mechanism suggests that the decrement in the drain current was due to the reduction of Cd²⁺ ions on the g-C₃N₄ surface which generates negative redox potential at the gate terminal while exposing the functionalized HEMT to Cd²⁺ ions. Hence, a simple, miniaturized, sensitive and real-time sensor has been developed using AlGaN/GaN HEMT functionalized by g-C₃N₄ to detect Cd²⁺ ions in an aqueous environment.