Modeling of Graphene Based Enzyme Field Effect Transistor with Ppy/K/CNT as Sensing Layer for Cholesterol Detection

Abstract

A physical model for graphene based enzyme field effect transistor (G-ENFET) for cholesterol detection has been developed. The device replaces silicon substrate with p-type graphene substrate and uses heavily doped n-type graphene for source and drain regions. ZrO2 having high dielectric constant is used as gate insulator and the sensing membrane for the substrate (cholesterol) on which the enzyme cholesterol oxidase (ChOx) is immobilized is made up of a composite of potassium doped carbon nanotube with polypyrrole (PPy/K/CNT). The modeling of the device has been done by considering various potentials in the device from which a set of equations are derived that characterize the electrolyte enzyme insulator semiconductor (EEIS) structure. The output is measured in terms of drain current variations at different cholesterol concentrations. A comparison between the experimental results of the fabricated device with the modeling results gives a good fit.