Performance analysis based on biomolecule position and pH-sensing mechanism for vertical TFET

Abstract In this study, the impact of the diffusion mechanism of a biomolecule in the nanocavity ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>b</mml:mi> <mml:mi>i</mml:mi> <mml:mi>o</mml:mi> </mml:mrow> </mml:msub> </mml:math> ) region on the electrical characteristics of a split-gate, step-channel electrolyte-insulated semiconductor vertical TFET (SGSC-EIS-VTFET) pH biosensor was investigated. The impact of the transport sensing mechanism, that is, diffusion-limited process and rapid mixing process of biomolecules in the nanocavity sensing area, on the pH of the analyte was also examined. Physics-based modelling was used to determine the interface charge density at the oxide-silicon interface of the proposed vertical TFET pH biosensor. We also considered the effect of pH values on the proposed device performance, like drain current ( I ds ), transconductance (gm), current sensitivity (S ID ), and voltage sensitivity (S V ) after the inclusion of electrolyte medium. Here, the maximum S V ∼ 145 mH pH −1 for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>b</mml:mi> <mml:mi>i</mml:mi> <mml:mi>o</mml:mi> </mml:mrow> </mml:msub> </mml:math> = 6 nm, which is higher than the Nernstian limit (59.2 mV pH −1 ), and S ID has been enhanced by 10 times per pH variation. This study indicated that the diffusion of biomolecules significantly impacts the performance parameters of the proposed structure because of the realistic dominance of the sensing mechanism and the conjugation of analyte on the sensing area.