Drift and Hysteresis Effects on AlN/SiO2 Gate pH Ion-Sensitive Field-Effect Transistor

The nonideal and unstable factors of AlN-based ion-sensitive field-effect transistor (ISFET) devices including the drift and hysteresis effects have been investigated in this study. The drift and hysteresis of AlN-based pH-ISFET devices have been measured using a constant current constant voltage (CCCV) readout circuit. The drift rates were obtained by long-time monitoring for 12 h in pH = 1, 3, 5, 7, 9, and 11 buffer solutions, which indicated that the drift rate increased with the pH value. The hysteresis effect was investigated by exposing the AlN gate ISFET in pH = 7-3-7-11-7 loop cycles with loop times of 960s, 1920s and 3840s, and the magnitudes of hysteresis of 1.0, 1.5 and 4.5mV were obtained, respectively. The temperature coefficient of hysteresis was found to be approximately 0.234mV/°C. In addition, it was also found that the hysteresis width with pH started from acid side is smaller than that started from basic side, which results in an asymmetric hysteresis effect.