Impact of trap states and steric effects on Ge-source V-TFET based pesticide biosensor
摘要
This paper presents a vertically tunneled Ge-source TFET pesticide biosensor in which device design, pesticide–HfO₂ interaction, and realistic non-idealities collectively determine sensing performance. The vertical band-to-band tunneling junction is modulated by adsorption of glyphosate molecule on the HfO2 surface. The influence of biomolecular charge density (–3 × 1013, 0, + 3 × 1013 cm2) is examined in terms of drain current, surface potential, subthreshold slope, Ion/Ioff, sensitivity, and linearity metrics such as IIP3, VIP3, and IMD3. The results show that positive biomolecular charge enhances band bending and carrier injection, resulting in improved tunnelling efficiency and higher sensitivity, whereas negative charge increases the tunnelling barrier and weakens the sensing response. Fill-factor analysis indicates that increased biomolecular occupancy strengthens electrostatic coupling and improves sensitivity. Positional analysis further shows that biomolecules located near the gate oxide/sensing region provide stronger channel-potential modulation and higher sensitivity. The effect of trap-assisted tunnelling is evaluated for semi-filled cavity configurations, where TAT modifies the total drain-current response and enhances Ids sensitivity in selected cases. Steric and repulsive steric effects significantly alter effective capacitance, electric-field distribution, tunnelling behavior, and sensing accuracy, revealing a trade-off between electrostatic current enhancement and chemical sensing sensitivity. This study shows that optimization of biosensor structure, analyte arrangement, fill factor, and trap mitigation is essential for reliable and high-performance pesticide detection.