Label-Free Detection of Thyroid Cancer Biomarkers Using Heterojunction GAA Ferroelectric p-n-i-n TFET Biosensor.

The global rise in thyroid cancer incidence has intensified the demand for reliable, rapid and minimally invasive diagnostic tools as current clinical practice often result in unnecessary surgical procedures for benign thyroid nodules. In this context, this work proposes a highly sensitive label-free biosensor, based on a heterojunction gate-all-around ferroelectric p-n-i-n tunnel field effect transistor (HJ-GAA-Fe p-n-i-n TFET) for early thyroid cancer detection. The sensing mechanism leverages variations of the dielectric properties and charge states of thyroid cells, which modulates electrostatic environment of the device. A ferroelectric gate stack introduces a negative capacitance effect that amplifies biomolecule induced electrical perturbations, while a nanocavity beneath the gate metal provides a dedicated region for thyroid cell immobilization. TCAD based simulations are used to evaluate clinically relevant sensitivity metrics including drain current, ON-OFF current ratio and threshold voltage. Furthermore, the proposed biosensor's reliability is assessed through response time, limit of detection (LOD), temperature stability, fill factor variation, early-stage detection capability, steric hindrance effect and noise immunity. The influence of both charged and neutral thyroid cancer cells is systematically analyzed. The proposed biosensor achieved a drain current sensitivity of $5.2\times 10^{{8}}$ , an ON-OFF ratio sensitivity of $3.23\times 10^{{6}}$ , a threshold voltage shift of 0.25 V, and selectivity of 12.41 of cancerous thyroid cells, indicating strong potential for accurate and early thyroid cancer diagnostic purpose.