Design and analysis of high-performance double-gate ZnO nano-structured thin-film ISFET for pH sensing applications

Abstract

This paper reports a high-performance double-gate zinc-oxide thin-film ion-sensitive field-effect transistor (DG-ZnO-ISFET) for pH sensing applications. The sensing mechanism of DG-ZnO-ISFET and a simulation model for pH sensing analysis are demonstrated herein. Various aspects of the device are elucidated through the study of channel conductance, electron density, energy band, and surface-potential profiles. The DG-ZnO-ISFETs enhance minor surface potential variations by capacitive coupling across the dielectrics of the top and bottom gates. Further, it operates by altering the bottom-gate voltage (VBG), obviating the need for a reference electrode system. The device depicts enhanced voltage sensitivity of 205.57 mV/pH, which is substantially 3.48 × greater than the Nernst limit sensitivity. In addition, the DG-ZnO-ISFET renders a maximum current sensitivity of 10.82 mA/mm.pH at VBG=5V. Furthermore, it exhibits high linearity in both voltage and current sensitivity, with the coefficient of determination (R2) values of 0.984 and 0.964, respectively. With their increased sensitivity and linearity, DG-ZnO-ISFETs have the potential device for next-generation biosensors.