Effect of MoS₂ layers on the performance of FET-based biosensors: a comprehensive study

Abstract MoS 2 -based transistors have attracted significant attention in several sensing applications owing to their ultra-thin structure and high mobility. In this work, the performance of MoS 2 field-effect transistor-based biosensors (BioFETs) was systematically analysed with device-level modelling, considering different biomolecules such as uricase, streptavidin, cholesterol oxidase (ChOx), and aminopropyltriethoxysilane (APTES). The BioFETs were modelled utilizing appropriate physics related to the site-binding principle, the surface charge density of biomolecules, and the transport of diluted species in electrolytes. First, MoS 2 -based field-effect transistors with different top-oxide materials were evaluated for pH sensing, where HfO 2 provided a near-Nernstian voltage sensitivity of 58.88 mV pH −1 . Additionally, a MoS 2 -based BioFET model was developed with biomolecules on top of the HfO 2 surface and analysis was carried out for single- and double-gated (DG) configurations. BioFET performance was evaluated based on drain-to-source current, subthreshold swing, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mtext mathvariant="italic">I</mml:mtext> <mml:mrow> <mml:mi>ON</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:msub> <mml:mtext mathvariant="italic">I</mml:mtext> <mml:mrow> <mml:mi>OFF</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> , and voltage sensitivities. The effect of the MoS 2 layers on the performance of the BioFET was analysed. For the monolayer MoS 2 -based BioFET, a maximum top-gate voltage sensitivity ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mtext mathvariant="italic">S</mml:mtext> <mml:mrow> <mml:mi>TV</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> ) of 129.95% and a bottom-gate voltage sensitivity ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mtext mathvariant="italic">S</mml:mtext> <mml:mrow> <mml:mi>BV</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> ) of 254.55% were obtained for APTES. However, the performance of a quadlayer MoS 2 -based BioFET in a DG configuration ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mtext mathvariant="italic">S</mml:mtext> <mml:mrow> <mml:mi>BV</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:mrow> </mml:math> of 221.69% for APTES) was comparable to that of a monolayer MoS 2 -based BioFET. Overall, this work highlights the significant role of MoS 2 layers and gate configurations for BioFET performance in sensing applications.