Ultrasensitive and Reliable Extended-Gate Field-Effect Transistors for Ions Detection with a Dual-Gate Structure

Measuring and evaluating ion levels in body fluids is crucial for human health diagnostics. Herein, we implemented a dual-gate structure to enhance the ion sensitivity of extended-gate field-effect transistors (EGFETs). The extended gate serves as an ion detector, while an indium-gallium-zinc-oxide (IGZO) thin-film transistor (TFT) functions as the transducer. The IGZO TFT was engineered with a high-k top gate insulator (HfO₂) and a low-k bottom gate insulator (SiO₂), which effectively improves capacitive coupling and significantly enhances signal amplification. This results in an amplification coefficient (ΔV_BG/ΔV_TG) of up to 29. Leveraging the exceptional signal amplification capability of the dual-gate configuration, our EGFET exhibits ultrahigh sensitivity for both cation (H⁺) and anion (Cl⁻) detection, with values of 1.66 V/pH and 1.63 V/dec, respectively. Furthermore, the EGFET with a dual-gate structure demonstrates remarkable stability over a long period. These outstanding ion-sensing capabilities endow our device with significant potential for diverse analytical and biomedical applications.