Analysis of Hetero-Stacked Source TFET and Heterostructure Vertical TFET as Dielectrically Modulated Label-Free Biosensors

This paper reports an extensive comparison of a hetero-stacked source tunnel field effect transistor (TFET) and heterostructure vertical TFET as label-free biosensors based on dielectric modulation. Due to the difference in the TFET design, the vertical TFET possess highrer sensitivity, ON-state current, $\text{I}_{ON}/\text{I}_{OFF}$ ratio and a lower subthreshold swing. Comparative analysis is carried out using technology computer aided design (TCAD) simulator where the sensitivity of the biosensors has been studied taking into consideration neutral and charged biomolecules for various dielectric constant values. Study of the phenomenon of steric hindrances and probe irregular placements provide better understanding of non-ideal state of the sensors. Due to the structural differences between the biosensors, decreasing step profile exhibits the highest sensitivity for hetero-stacked source TFET biosensor whereas increasing step profile shows the highest sensitivity for heterostructure vertical TFET biosensor. For a particular dielectric constant value of the biomolecule, the vertical based TFET biosensor is 10 ⁴ times higher in terms of sensitivity as compared to the hetero-stacked source TFET biosensor when considering steric hindrances. Finally, the biosensors are benchmarked against other published literatures and it shows that the sensitivity of the heterostructure vertical TFET biosensor is overall higher than other FET based biosensors.