Bilayer indium gallium zinc oxide electrolyte-gated field-effect transistor for biosensor platform with high reliability

Abstract

The electrolyte-gated indium gallium zinc oxide field-effect transistor (IGZO-EGFET) has advantages for use in biosensors; e.g., it is label-free and has a high sensitivity, low cost, and low power consumption. However, the reliability of IGZO-EGFET under various conditions has not been proven. In this study, we demonstrate a bilayer IGZO-EGFET with high reliability and reproducibility under various pH and buffer conditions regardless of the surface functionalization. The bilayer of IGZO developed in situ by controlling the O2 pressure during deposition has a varying number of O vacancy-related trap sites. The top layer having less O vacancies provides a self-passivation effect, whereas the bottom layer with more O vacancies acts as the active layer of the device. The bilayer IGZO-EGFET exhibits not only high chemical stability but also very little pH-hysteresis upon cyclic variation of the pH. Moreover, it exhibits a reliable and reproducible signal in phosphate buffer solutions with different concentrations, even after surface functionalization. The biotin-functionalized bilayer IGZO-EGFET exhibits a selective sensitivity for streptavidin, with a linear relationship of 10.7 mV/dec. The proposed bilayer IGZO-EGFET structure is expected to be used as a platform for various biosensing devices.