Demonstration of extended-gate structure for pH sensors based on amorphous indium-gallium-zinc oxide thin-film transistors

Abstract

For the purpose of improving reliability of our high-sensitivity pH sensor based on the top-gate effect in amorphous indium-gallium-zinc oxide thin-film transistor (a-InGaZnO TFT), we propose extended-gate a-InGaZnO TFT pH sensor having an ALD-AlOx/sputtered-TaOx layered top-gate insulator and a Ti extended-gate electrode. Unlike our previous insulated-gate a-InGaZnO TFT pH sensor, we do not need to immerse the TFT sensor device into the solution, and thus we could expect improvement of its reliability. We discuss our primary results for the extended-gate a-InGaZnO TFT pH sensor, including its pH sensitivity and response to a pH change of 0.05.