DESIGN AND SIMULATION OF NOVEL NANO-SCALE DEVICES FOR BIOSENSOR APPLICATIONS

Abstract

Field Effect Transistor (FET)-based biosensors have become a cornerstone in biomedical diagnostics, environmental surveillance, and biosecurity because of their exceptional sensitivity, fast response time, and compact design. These biosensors utilize the intrinsic characteristics of FETs to identify biological and chemical sub- stances by observing variations in electrical parameters such as current or voltage. Among the various FET-based biosensors, silicon nanowire (SiNW)-based biosen- sors are particularly noteworthy. The substantial surface-to-volume ratio of SiNWs greatly amplifies their interaction with target biomolecules, enhancing sensitivity and lower detection limits. Furthermore, the compatibility of SiNWs with existing semi- conductor fabrication technologies facilitates their integration into complex sensing systems. This thesis investigates various FET-based devices, including Charge Plasma Tun- nel FETs, Non-Reconfigurable Silicon Nanowire (SiNW) FETs, and Reconfigurable SiNW FETs, focusing on their promising uses in biosensing. Initially, a sensitivity analysis of CP Tunnel FETs (CP-TFETs) was conducted by optimizing cavity place- ment and size to boost biosensor performance. The study then focuses on biosensors utilizing Silicon Nanowire FETs, examining reconfigurable and non-reconfigurable types. This evaluation covers calibration, sensitivity parameter analysis, and a per- formance comparison with cutting-edge biosensors. Additionally, Spacer Engineering techniques are applied to enhance the performance of RFET-based biosensors. Fol- lowing this, noise and sensitivity analysis was performed, assessing distortion and linearity. An analytical model was formulated for RFET-based biosensors and its sensitivity compared to leading biosensors. Below, comprehensive assessments of the viii effectiveness of each device for biosensing are provided. Optimizing Cavity Position in the Charge Plasma Tunnel FET-Based Biosensor: We performed a comparative analysis of different cavity positions (source, gate, and drain) in CP-TFET for biosensor applications. The intrinsic properties of biomolecules, such as the dielectric constant and charge density, are leveraged to detect biomolecules within the nanogap cavities. Our findings indicate that the placement of cavities significantly impacts the device’s sensitivity and electric field distribution, suggesting optimal configurations for enhanced biosensing performance. Performance Evaluation of Reconfigurable FET (RFET) and Non-Reco- nfigurable FET for Biosensor Application: We assessed the SiNW FET-based biosensor with and without reconfigurable features and examined the sensitivity of the proposed biosensors. Furthermore, we compare the sensitivity of our proposed device with that of the advanced FET-based biosensors. High-Performance RFET-based Biosensor using Spacer Engineering: We explored the Spacer Engineering Reconfigurable Silicon Nanowire Schottky Bar- rier Transistor (SE R-SiNW SBT) as a label-free biosensor capable of detecting dual- polarity biomolecules with high sensitivity, selectivity, and linearity. The device’s dual-gate configuration significantly enhances the modulation of the Schottky tun- neling width and channel potential, providing a robust framework for biosensing ap- plications. Noise and Sensitivity analysis of the RFET for Biosensor Application: This work presents a comprehensive noise and sensitivity analysis of the proposed RFET tailored for biosensor applications. Experimental calibration corroborates the simulation results, showcasing the device’s exceptional sensitivity and noise char- acteristics. The findings underscore the proposed RFET’s potential for real-time, low-power biosensing applications. ix Analytical Modeling of the RFET for Biosensor Application: The analyt- ical modeling of the proposed RFET biosensor, featuring a cavity under the control gate, is introduced to further advance biosensing capabilities. This design leverages the dielectric modulation effect to achieve high sensitivity and selectivity in detect- ing biomolecules. The device’s architecture and operation are optimized to enhance biosensing performance, showcasing significant potential for various biosensing appli- cations.