Analytical Modeling of Negative Capacitance Field-Effect Transistor for Highly Sensitive Biosensor Applications

The subthreshold swing (SS) of conventional field-effect transistors (FETs) is fundamentally limited to 60 mV/dec at room temperature, which significantly constrains the sensitivity of biosensors in detecting weak biological signals effectively. To address this bottleneck, we present a comprehensive, physics-based, and circuit-compatible analytical model for a 2-D material negative capacitance FET (NCFET) biosensor. The model features a top-gate architecture incorporating a HfZrO (HZO) ferroelectric layer for the first time, designed to be fully compatible with standard semiconductor fabrication processes. It provides a robust theoretical framework for accurately predicting the performance of NCFET biosensors (NC-BioFET) and addresses the limitations of traditional FETs. Using an n-WSe2 NCFET biosensor as an example, we validate the model through extensive simulations, achieving an SS as low as 30 mV/dec and demonstrating excellent pH sensing performance. In a model-constructed aqueous environment, the sensor exhibits an impressive pH detection sensitivity of 1799/pH, significantly outperforming the 461/pH sensitivity observed in its conventional FET biosensor. Furthermore, to validate the accuracy of the model, we fabricated WSe2 NCFET biosensors and tested their response across a range of pH. The model shows excellent agreement with experimental results in terms of drain current, SS, and voltage/current sensitivity. This work establishes a robust theoretical and experimental foundation for the design and optimization of high-performance and low-power biosensors. It also bridges the gap between NCFET technology and biosensing applications, paving the way for next-generation biosensors with ultrahigh sensitivity and superior signal detection capabilities.