Capacitance modeling, simulation and RF characterization of horizontal floating gate field effect transistor (H-FGFET) for gas sensing application

Abstract

In this paper, physics-based capacitance model has been developed for horizontal floating gate field effect transistor (H-FGFET). The horizontal design of floating gate (FG) FET allows detection of large gas molecules like nitrogen dioxide (NO2), sulphur dioxide (SO2), hydrogen sulfide (H2S), carbon dioxide (CO2) etc. In order to validate the proposed model, the device has been designed using Sentaurus TCAD simulator and results have been validated with experimental data. Different electrical parameters such as transfer characteristics, switching ratio, output characteristics, threshold voltage, drain induced barrier lowering (DIBL), C-V characteristics, transconductance, output conductance and RF characteristics of the device have been analyzed at room temperature. The simulation result shows that increase in channel length of H-FGFET results in decreased leakage current, improved switching performance, increased gate capacitance and reduced DIBL. The comparative analysis of H-FGFET with previously reported floating gate FET structures reveal that proposed device offers highest switching ratio. The RF characteristics of H-FGFET illustrates that proposed device can operate efficiently as an amplifier for the frequency range of 0.1 GHz to 100 GHz. Further, the proposed device has also been tested for the detection of nitrogen dioxide gas and results reveal that with increase in operating temperature from 30 °C to 180 °C the leakage current of the device increases from 10−13 to 10−9 and OFF current sensitivity of the proposed sensor changes by 82% on changing the work function of sensing layer from 50 meV to 250 meV.