Low-Voltage InGaZnO Ion-Sensitive Thin-Film Transistors Fabricated by Low-Temperature Process

In this brief, we developed a low-voltage ( V_DS =0.5 V and V GS = 0.8 V) InGaZnO ion-sensitive thin-film transistor (ISTFT) sensor using a high- κ HfO₂ sensing membrane grown by lowerature atomic layer deposition. The InGaZnO TFT exhibited a low threshold voltage of 0.2 V, a high field-effect mobility of 5.9 cm²/V-s, a small subthreshold swing of 90 mV/decade, and high I scriptscriptstyle ON I scriptscriptstyle OFF ratio of 2.4 × 10⁷. The pH sensor based on an InGaZnO ISTFT device exhibits a high sensitivity of 60.5 mV/pH and good linearity in the pH range from 3 to 11. Moreover, such a pH ISTFT sensor presents a hysteresis width of 8 mV after a pH loop of 7→ 4→ 7→ 10→ 7 and a low drift rate of 2.5 mV/h at pH 7.