High-Sensitivity In-Built N+ Pocket Electrically Doped Tunnel FET Biosensor with Nanogap Cavity

This study innovatively proposes a high-performance biosensor based on an in-built N⁺ pocket electrically modulated tunnel field-effect transistor (ED-TFET). The device employs a dual-polarity-gate-modulated PN architecture, achieving electrostatic induction of a N⁺ pocket region at the source-channel interface through the synergistic electrical regulation of a control gate (CG) and polarity gates (PG1/PG2). By applying reverse bias voltages of -1.2 V and +1.2 V to PG1 and PG2, respectively, a functionalized region with steep doping gradients is successfully constructed. This gate-controlled carrier dopping strategy overcomes the limitations of conventional doping processes, significantly enhancing doping precision while avoid thermal budget constraints caused by high-temperature annealing, thereby providing an innovative solution for simplifying device fabrication. To enable specific biomolecular detection, a nanoscale cavity is fabricated near the source-side PG1 dielectric layer. Multidimensional electrical parameter analysis systematically investigates the modulation effects of neutral within the cavity. Simulation characterization reveals high Ids sensitivity ($7.13 \times 10^{12}$) when the cavity is fully occupied by biomolecules with a relative permittivity ($k=12$), accompanied by an ultralow subthreshold swing of $24.3 \mathrm{mV} / \mathrm{dec}$. The effect of cavity geometry and filling factor on the nonlinear adjustment of detection sensitivity is also discussed.