Performance analysis of SiGe source based heterojunction TFET biosensor for improved sensitivity

This work presents a novel SiGe-source-based heterojunction tunnel field-effect transistor (TFET) biosensor that incorporates a nanogap dielectric cavity beneath the gate and a hetero-dielectric BOX (HDBOX) structure for ultra-sensitive, label-free detection of both neutral and charged biomolecules. The proposed device architecture leverages a low-bandgap SiGe source to enhance band-to-band tunneling (BTBT) efficiency and utilizes dielectric modulation in the nanogap cavity to enable electrostatic coupling with immobilized biomolecules. The sensor exploits distinct detection mechanisms—dielectric constant variation for neutral biomolecules and combined dielectric and charge-field modulation for charged species—thereby achieving a comprehensive detection capability. Extensive TCAD simulations, calibrated against experimental TFET data, were conducted using Kane’s BTBT model, Lombardi mobility, Fermi–Dirac statistics, and SRH recombination, under room temperature conditions. The device demonstrates a high ON/OFF current ratio of 1.947 × 10⁸, a steep subthreshold slope of 28.57 mV/decade, and a maximum current-based sensitivity (SID) of 1.548 × 10⁸ for a dielectric modulation range of κ = 1 to 26. Compared to state-of-the-art DM-TFET and PNPN-TFET biosensors, the proposed design exhibits significantly improved sensitivity, lower off-state leakage (~ 10^–14 A), and reduced process complexity. While this study is simulation-based, the device structure employs CMOS-compatible materials and fabrication techniques, paving the way for future experimental validation. These results position the HDBOX TFET biosensor as a promising candidate for real-time, low-power, and label-free biomedical diagnostics.