Sensitive and Selective Detection of Pb 2+ Ions Using 2,5-Dimercapto-1,3,4-Thiadiazole Functionalized AlGaN/GaN High Electron Mobility Transistor

We report sensitive and selective AlGaN/GaN High Electron Mobility Transistor (HEMT)-based sensor for Lead ion (Pb ²⁺ ) detection. The gate region of the HEMT was functionalized by 2,5-dimercapto-1,3,4-thiadiazole (DMTD). The response of the sensor is observed by monitoring drain to source current ( $\text{I}_{\textsf {DS}}$ ) for different concentrations of Pb ²⁺ ions at a fixed drain to source voltage ( $\text{V}_{\textsf {DS}}$ ). Our sensor reaches the lower detection limit of 0.018 ppb, which is much lower than the standard detection limit recommended by the World Health Organization (WHO) for drinking water. Furthermore, the sensor exhibited a rapid response time of ~4 seconds and high sensitivity of $0.607~\mu \text{A}$ /ppb. Moreover, the selectivity analysis was performed and found that the sensor was highly selective towards Pb ²⁺ ions. The change in electron concentration at 2-dimensional electron gas (2DEG) upon the capture of Pb ²⁺ ions at gate region by DMTD, causes a change in the $\text{I}_{\textsf {DS}}$ , which showed excellent sensing response towards Pb ²⁺ ions. The highly sensitive, selective, and rapid detection of Pb ²⁺ ions paves the way for stable sensing performance based on DMTD functionalized AlGaN/GaN HEMT sensor.