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-kappa HfO2 sensing membrane grown by low-temperature atomic layer deposition. The InGaZnO TFT exhibited a low threshold voltage of 0.2 V, a high field-effect mobility of 5.9 cm(2)/V-s, a small subthreshold swing of 90 mV/decade, and high I-ON/I-OFF ratio of 2.4x10(7). 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.