Sensitivity and Non-Ideal Issues Analysis of a Dielectric-Modulated Electrically Doped Junctionless TFET-Based Label-Free Biosensor

To reduce the fabrication complexity and cost of nanoscale biosensors, a novel electrically doped concept is proposed for the first time, aiming to implement a dielectric-modulated junctionless tunnel field-effect transistor (DM-ED-JLTFET) for label-free biomolecule detection. The n+ drain and p+ source regions in the proposed device are induced by applying a bias of polarity gate-1 (PG-1) = +1.2 V and PG-2 = -1.2 V, respectively, over the ultrathin silicon body. A nanogap cavity beneath the PG-2 terminal is formed by etching a part of the dielectric oxide layer toward the tunneling interface to capture the biomolecule test sample. The existence of neutral and charged molecules in the cavities has been investigated using changes in the electrical characteristics of the proposed biosensor, such as drain current, energy band, and electric field. The sensing performance of the proposed biosensor is evaluated in terms of drain current (
${I} {_{\text {DS}}}$
), subthreshold swing (SS), threshold voltage (
${V} {_{\text {Th}}}$
), switching ratio (
${I} {_{\text {ON} }}/{I} {_{\text {OFF} }}$
), and transconductance-to-current ratio (
${g} {_{\text {m}}}/{I} {_{\text {DS}}}$
). The proposed DM-ED-JLTFET biosensor achieves a maximum sensitivity of
${5.58} \times {10}^{{10}}$
with a fully filled nanogap for a neutral biomolecule with a dielectric constant of 12. The effects of non-ideal issues on sensitivity, such as different fill factors (FFs) and steric hindrances, are also studied of the proposed biosensor to understand the practical challenges.