Low-Voltage Feedback Field Effect Transistor based Ion-Sensing: A Novel and Detailed Investigation for energy-efficient pH Sensor

In this work, we present simulation-based results of a vertical nanowire feedback field effect transistor as an ion-sensor (ISFBFET) for accurate pH detection. The sensing mechanism of the investigated ISFBFET draws upon the principles of the Gouy-Chapman-Stern layer and the site-binding model. Along with SiO2 only, the deposition of Al2O3 on SiO2 as a sensitive layer is investigated. Sensitivity parameters are obtained from snap-back characteristics and are evaluated against work function (ΦG) engineering. At optimized conditions, ISFBFET results in ION/IOFF = 1010 and an SS = 0.03mV/dec with Al2O3-SiO2 improving the ION/IOFF by a factor of 1.24 (ΦG = 4.7eV) and 5.53 (ΦG = 5.1eV) over an oxide only gate insulator. Up to ΦG≤4.3eV, the sensing response of SiO2 is marginally better; whereas for ΦG> 4.3eV, Al2O3-SiO2 has a better sensing response. Peak sensitivity for Al2O3 is observed at ΦG = 4.7eV, maximum constant current and voltage sensitivity observed is 3927 and 2.73 respectively. In the near future, due to low power functioning, steeper response, and high sensitivity, Al2O3-SiO2 based ISFBFET can replace conventional oxide-based ion sensors for pH detection in commercial applications.