Super-Nernstian WSe₂/MoS₂Heterostructure ISFET Combining Negative Capacitance and Charge Screening Effects

We propose an ultra-scalable, highly sensitive, and label-free pH sensor by incorporating a negative capacitance (NC) effect with a 2-D WSe2/MoS2 heterostructure-based ion-sensitive field effect transistor (ISFET). The combination of electrostatic screening in 2-D WSe2/MoS2 heterostructure with the inclusion of the NC effect in the fluid gate offers tremendous enhancement in sensitivity. The sensor performance is evaluated by combining the numerical solutions of the 1-D Landau-Khalatnikov (L-K) equation with the experiment-calibrated technology computer-aided (TCAD) simulations of the WSe2/MoS2 ISFET. The proposed device shows a maximum voltage sensitivity of 4.38 V/pH with excellent noise performance leading to an enhanced resolution of 0.002 units of pH. The NC-WSe2/MoS2-ISFET demonstrated ∼ 15 × and ∼ 8 × improvement in sensitivity, respectively, when compared to WSe2/MoS2 and NC-WSe2 baseline ISFET counterparts. The device design is amenable to scaling due to the use of an atomically thin 2-D channel and ultrathin layer of high-k (HfO2) gate dielectric. The use of the NC effect in a 2-D heterostructure ISFET paves the way for the next generation of highly sensitive and label-free biosensors for point-of-care diagnostics.