A high-performance Si0.5Ge0.5 source vertical nanowire TFET for ultra-sensitive biosensing and high-speed comparator applications

Abstract

In this work, a SixGe1−x source-engineered vertical nanowire tunnel field effect transistor (VNW-TFET) is proposed and systematically investigated for biosensing and circuit applications. The effect of Ge mole fraction (x = 0–0.9) is analyzed, and it is observed that the Si0.5Ge0.5 configuration exhibits optimal performance, providing a balanced trade-off between enhanced band-to-band tunneling and controlled leakage current. Based on this optimized structure, a dielectrically modulated biosensor is designed, and its performance is evaluated for different dielectric constants (k = 2.1–12). The results show that the device sensitivity increases significantly with k due to enhanced electric field and tunneling probability, achieving a maximum ION sensitivity of 2036 and ION/IOFF sensitivity of 1.6 × 106. Further, device optimization is performed by varying key parameters such as cavity thickness (2–2.4 nm), cavity length (24–36 nm), temperature (200–400 K), and drain voltage (0.4–1.4 V). It is observed that reduced cavity thickness enhances performance, while cavity length has minimal impact, confirming that sensing is dominated by the tunneling region. The device also exhibits stable operation under temperature variations. To validate circuit-level applicability, the proposed device is modeled in Verilog-A and implemented in Cadence to design a comparator circuit. The comparator achieves a slew rate of 5 MV μs−1, propagation delay of 242 ps, dynamic power of 112 mW, and static power of 28.6 μW. The proposed Si0.5Ge0.5-VNW-TFET demonstrates excellent performance in terms of sensitivity, speed, and power efficiency, making it a promising candidate for next-generation biosensing and low-power circuit applications.