Design and analysis of a vertically extended gate field effect transistor (VEG-FET)-based hydrogen gas sensor: a comprehensive modeling and simulation approach

In this study, a novel vertically extended gate field effect transistor (VEG-FET)-based hydrogen (H₂) gas sensor with a look-up-table (LUT) based modeling and simulation approach is presented. The gate area is extended vertically without affecting the intrinsic parameters to provide a larger area for the adsorption of H₂ molecules without increasing the sensor footprint. The gate electrode was vertically extended by depositing platinum (Pt) over a channel created in Parylene-C polymer. An analytical model was constructed for the interaction of H₂ gas with platinum (Pt) to determine the change in the work function (Φ_M). The Pt work function lowered by 16% for input hydrogen gas pressure (P_H2) of 0 to 0.5 torr. The Pt-H₂ interaction information is passed to a technology computer-aided design (TCAD) tool for VEG-FET design and simulation. The drain current (I_DS) of the VEG-FET varies from 150.7 mA without H₂ gas to 310.3 mA at 0.5 torr hydrogen gas pressure at gate to source (V_GS) and drain to source (V_DS) voltage of 3 V. Both bioreaction and TCAD results are passed to Cadence Virtuoso for a complete gas sensor with read-out circuit simulation using the LUT method. A VEG-FET based common source amplifier with resistive load was designed and simulated, and the output voltage (V_out) varied by ∼40% for P_H2 = 0.5 torr.