Design and Modeling of the Electrostatically Controlled Nanowire FET for Ppt-level Hydrogen Sensing

Abstract We present the design of a H 2 gas sensor based on palladium (Pd) decorated silicon-on-insulator (SOI) nanowire field effect transistor (FET) with a standard SOI complementary metal-oxide-semiconductor fabrication process, where a top Pd layer plays a dual role of a catalyst and a surrounding metal gate. A numerical study was conducted based on a simplified steady-state model to describe the sensing mechanism of H 2 in dry air at 300 K. The simulation is based on the model of dissociative H 2 adsorption on the Pd surface and the formation of a dipole layer at the Pd/SiO 2 interface. The H atoms induced dipoles lead to a potential drop which exponentially increases the FET drain current and consequently, the sensor response. The FET drain current is controlled by its back-gate bias and by varying the H 2 concentrations; it is shown that the drain current response reaches 1.8 × 10 8 % for 0.8% H 2 in air and a superior sensitivity of 4.58 × 10 4 %/ppm in the sub-threshold operation regime. The sensor exhibits an outstanding theoretical detection limit of 50 ppt (response of 1%) and an upper dynamic range limit of 7000 ppm which allow for timely and accurate detection of H 2 gas presence. The power consumption ranges between ∼10 fW (dry air) to ∼20 nW (0.8% H 2 in dry air) and therefore paves the way for a very large-scale integration commercial sensing platform.