Sensitivity enhancement of amorphous InGaZnO thin film transistor based extended gate field-effect transistors with dual-gate operation

Amorphous indium–gallium zinc oxide (a-IGZO) based TiO2 extended gate field-effect transistors (EGFETs) with a high pH sensitivity of 129.1 mV/pH beyond the Nernst response limit were realized by the dual gate operation mode. The capacitive coupling between the front and bottom gate dielectric for the DG operation greatly improved its sensitivity as well as its chemical stability. The developed high performance pH sensor was rooted in outstanding electrical characteristics of an a-IGZO thin film transistor with an on/off current ratio of 3.7 × 107, a subthreshold swing of 86 mV/dec, and a field-effect mobility of 17.62 cm2/V s.