Growth of a sputtered Ta2O5/ZnO film and its application to an ion-sensitive field-effect transistor

Abstract

High-performance and transparent ion-sensitive field-effect transistor (ISFET) was prepared by a facing-target type sputtering method using the combination of a ZnO layer for the channel and a high-k Ta2O5 layer for the gate insulator. The ISFET showed a high transconductance of 2.3 mS, a low drift current of <; ±0.5 μA/h, a small gate leakage current of <; 2 nA, and a small hysteresis width of ~0.1 V. The typical pH sensitivity was ~84 μA/pH and ~55 mV/pH, and the time-constant for pH change was as small as 10 s. These parameters are comparable with those of commercially available Si ISFETs.