A CIPS-based negative capacitance field-effect transistor biosensor with extended-gate structure

Biosensors based on field-effect transistor (FET) have advantages of label-free detection, rapid response, small size, and good compatibility with semiconductor manufacturing process. However, their sensitivities are limited by the Boltzmann distribution of electrons. Negative capacitance effect has the potential to address this challenge. Here, we realize two-dimensional (2D) van der Waals (vdW) heterojunction negative capacitance field-effect transistors (NCFETs) with MoS2 channel, CuInP2S6 ferroelectric layer, graphene contacts, hexagonal boron nitride dielectric layer, and graphene top gate. The devices exhibit excellent electrical performance with on–off ratio of 106 and subthreshold swing of 26 mV/dec. Due to the ultrasmall subthreshold swing value, the NCFET demonstrates a high pH detection sensitivity (675.8 pH−1), significantly outperforming the traditional 2D-material FET biosensors (445.5 pH−1). An extended-gate structure with TiN sensing membrane is connected with the MoS2 NCFET. This structure prevents leakage current between the solution and the gate dielectric, which can improve the stability of the biosensor. This work provides insights into the design of biochemical sensing platform. The observation of the negative capacitance effect in all-2D-material-based biosensor may stimulate further fundamental research and potential applications.