High-Sensitivity Ammonia Gas Sensor Based on Dual-Material Dopingless GAA Nanowire FETs

Abstract This work demonstrates a charge plasma-based Gate-All-Around (GAA) nanowire field-effect transistor (FET) for high-sensitivity ammonia (NH3) gas sensing. The proposed device utilizes palladium (Pd) and molybdenum (Mo) as gate metals, where Pd exhibits superior performance due to its strong catalytic interaction with NH3 molecules. The sensing mechanism is governed by adsorption-induced work function modulation at the metal-gate interface, leading to measurable changes in threshold voltage (Vth), ON-state current (ION), and OFF-state current (IOFF). A systematic work function variation from 50 to 200 meV reveals significant enhancement in sensing metrics, with the ION/IOFF ratio improving from 2.6 × 108 to 1.6 × 1011 for Pd. Furthermore, channel length scaling and dielectric engineering demonstrate improved electrostatic control, with HfO2 (~6.3%) achieving ~7.87% higher sensitivity compared to SiO2 (~5.84%). The proposed architecture offers excellent switching behavior, low leakage, and strong sensitivity, making it a promising candidate for low-power, high-performance NH3 sensing applications.