795. Design and analysis of a vertically extended gate field effect transistor (VEG-FET)-based hy…

Fig. 1 (a) Modeling and simulation flow chart for complete biosensor system with read-out circuit. (b) Equivalent capacitor model for VEG-FET gas sensor showing the dipoles at the Pt-SiO2 interface.

Pramod Martha, et al, J. Mater. Chem. C 13, 5110 (2025)
https://doi.org/10.1039/d4tc04574b

(1) The high-temperature requirement, larger area, and poor reliability remain concerns with MOS-based gas sensors.
(2) The inherent amplification property of MOSFET makes it suitable for low-level gas detection.
(3) The gas-surface interactions change the properties of the sensing material, which alters key MOSFET parameters like the work function of the gate, gate capacitance, and threshold voltage. These variations change the output drain current.
(4) A large sensor footprint and operating voltage are major challenges in TFT-type gas sensors.
(5) The gas interaction with sensing material or the FET behavior of most FET-type H2 sensors was modeled separately, which doesn’t represent and predict the sensor behavior correctly prior to fabrication.
(6) FET-based gas sensors operate by detecting interactions between gas molecules and a metal surface. When gas molecules are adsorbed onto the metal, attractive forces loosen their atomic bonds, causing the gas to dissociate into ions. These ions create a dipole moment that induces a small signal variation at the gate, changing the electric field in the channel. This change causes a shift in the work function, which changes the threshold voltage and modulates the device current.
(7) The probability of finding a site for adsorbance on the surface and the residence time constant are prime parameters of gas kinetics with respect to gas pressure.