Si–Ge based vertical tunnel field-effect transistor of junction-less structure with improved sensitivity using dielectric modulation for biosensing applications

Abstract

A dielectric modulation strategy for gate oxide material that enhances the sensing performance of biosensors in junction-less vertical tunnel field effect transistors (TFETs) is reported. The junction-less technique, in which metals with specific work functions are deposited on the source region to modulate the channel conductivity, is used to provide the necessary doping for the proper functioning of the device. TCAD simulation studies of the proposed structure and junction structure have been compared, and showed an enhanced rectification of 104 times. The proposed structure is designed to have a nanocavity of length 10 nm on the left- and right-hand sides of the fixed gate dielectric, which improves the biosensor capture area, and hence the sensitivity. By considering neutral and charged biomolecules with different dielectric constants, TCAD simulation studies were compared for their sensitivities. The off-state current I OFF can be used as a suitable sensing parameter because it has been observed that the proposed sensor exhibits a significant variation in drain current. Additionally, it has been investigated how positively and negatively charged biomolecules affect the drain current and threshold voltage. To explore the device performance when the nanogaps are fully filled, half filled and unevenly filled, extensive TCAD simulations have been run. The proposed TFET structure is further benchmarked to other structures to show its better sensing capabilities.