I-V hysteresis characteristics of nano-field effect transistor (nanoFET) sensor with a floating metal gate electrode

A sensor based on a nano-field-effect transistor (nanoFET) can detect airborne charged substances and biomolecules or in a liquid environment in real time and a label-free manner. The approach is based on the principle of chemical gating, which is induced by the adsorption of charged substances on the surface of the FET channel. This study involved the fabrication of a nanoFET sensor with a top metal-gate electrode structure and the analysis of its I-V characteristics to assess its repeatability with respect to detecting airborne anions. We show that the I-V characteristics of the nanoFET sensor with a top metal gate electrode are affected by the capacitive coupling between the top metal sensing gate and the bottom back-gate by double sweeping the back-gate voltage. The proposed method to refresh and reinitialize the sensor is proven experimentally by recording the hysteresis of the nanoFET sensor with the top metal gate electrode. Consequently, the nanoFET sensor with an electrode with a top metal sensing gate could be reset by sweeping the back-gate bias voltage of the nanoFET device and show that the proposed structure is essential to reinitialize the sensor after the measurement. These properties of the nanoFET device with the top metal gate electrode enable the nanoFET sensor to be reinitialized by using only back-gate voltage sweep, contrary to the sensor without the metal gate.