Steep-Subthreshold Bilayer Tunnel Field-Effect Transistor-Based Efficient pH Sensing: Performance Characterization and Optimization

This letter presents a simulation report on a modern, power-efficient, steep subthreshold slope (SS) electron-hole bilayer tunnel field-effect transistor (EHB-TFET) as an ion sensor. The effect of variation in channel thickness and work function engineering (of both top and bottom gates) on the transversal electron tunneling rate and I
_DS
–V
_GS
characteristics is also discussed. At optimized values, the EHB-TFET results in low I
_off
(=10
⁻¹⁸
A/μm) and SS of 13 mV/dec. The Gouy–Chapman–Stern and the site-binding model form the basis for assessing EHB-TFET's sensing mechanism. The top gate is assumed to be the controlling gate, and as the bottom gate insulator, along with SiO
₂
, the sensitivity response of ZrO
₂
and Ta
₂
O
₅
is also examined. The sensitivity behavior is evaluated in terms of threshold voltage, and it was observed that sensitivity is directly proportional to the surface potential. The highest sensitivity obtained is for ZrO
₂
followed by SiO
₂
and Ta
₂
O
₅
. Due to the evident advantages of EHB-TFET in the near future, it can be used as a low-power, quick-responsive, reliable ion sensor and can be used to replace conventional industrial sensors.