Enhanced Sensing Properties of Fully Depleted Silicon-on-Insulator-Based Extended-Gate Field-Effect Transistor with Dual-Gate Operation

Abstract

Fully depleted (FD) silicon-on-insulator (SOI)-based SnO2 extended-gate field-effect transistors (EGFETs) beyond the Nernstian limit of 59 mV/pH were realized by using the dual-gate (DG) operation. The thickness of buried oxide (BOX) of SOI-MOSFETs was adjusted to magnify the capacitive coupling effect between top and bottom gate oxides in DG operation. As a result, the separate SOI-MOSFETs with 750-nm-thick and 200-nm-thick buried oxide (BOX) showed pH sensitivities of 2037.1 and 554.2 mV/pH, respectively, far beyond the Nernstian limit of 59 mV/pH. Also, better stability characteristics, such as the hysteresis phenomenon and drift effect, are achieved from DG operation.