Super-Nernstian WSe<sub>2</sub>/MoS<sub>2</sub> Heterostructure ISFET Combining Negative Capacitance and Charge Screening Effects
Sooraj Sanjay, Fahimul Islam Sakib, Mainul Hossain, Navakanta Bhat
Abstract
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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 15\times $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 8\times $ </tex-math></inline-formula> 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 (HfO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{2}}{)}$ </tex-math></inline-formula> 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.