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. 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 960 s, 1920 s and 3840 s, and the magnitudes of hysteresis of 1.0, 1.5 and 4.5 mV were obtained, resp. The temperature coefficient of hysteresis was approximately 0.234 mV/C. In addition, the hysteresis width with pH started from acid side is smaller than that started from basic side, which results in an asymmetric hysteresis effect. 30 refs.