A High-Sensitivity Biosensor Based on a Negative-Capacitance-Assisted Ferroelectric (FE)–Dielectric (DE) Heterostructure

This manuscript investigates a biosensor based on a gadolinium (Gd)-doped hafnium oxide (HfO2) ferroelectric–dielectric (FE-DE) heterostructure for high-sensitivity, low-power biomolecule detection. The sensing cavity consists of a dielectric layer and a biomolecule-filled region, where different filling conditions (0%, 50%, 75%, and 100%) emulate realistic sensing environments. The dielectric properties of the biomolecule changes, which results in changes of the dielectric capacitance, thus improving capacitance matching with the ferroelectric layer and stabilizing the negative-capacitance effect. This intrinsic voltage amplification enhances the electrical response of the biosensor. Electrical characteristics, including charge–voltage, energy–charge, capacitance–voltage, and voltage amplification, were analyzed for biomolecules with dielectric constants ranging from 1 to 12. Higher-dielectric-constant biomolecules exhibited superior sensing performance; for example, gelatin (K = 12) achieved the highest sensitivity of 1.9632 at 100% cavity filling, along with the maximum voltage amplification. To evaluate the impact of amplification, the amplified dielectric voltage was applied to the gate of a 50 nm NMOS transistor. The enhanced gate voltage improved the drain current and transconductance and enabled a subthreshold swing below the conventional thermal limit of 60 mV/dec. A feasible fabrication plan is demonstrated to show the possible realization of the sensor system. These outcomes indicate that the proposed Gd-doped HfO2-based FE-DE heterostructure is capable of efficiently magnifying the dielectric changes caused by biomolecules, thus offering an encouraging framework for future low-power and high-sensitivity biosensing applications.