Electrochemical modeling of carbon nanotube based dual gated junctionless enzyme field effect transistor

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This paper presents the electrochemical modeling of carbon nanotube (CNT) based dual gated junctionless enzyme field effect transistor (ENFET). Modeling is done using the enzymatic reactions on the substrate biomolecules, diffusion phenomena of the main substrate in the electrolyte, acidic or basic reactions of the product in the electrolyte, the pH detection properties of ion-sensitive field effect transistor (ISFET) and the current transport model of dual-gated CNTFET. The diffusion phenomenon of the substrate in electrolyte is modeled by Fick's law of diffusion. The acidic or basic reactions of the product yields hydrogen (H+) or hydroxyl ions (OH−) in the solution which results in pH variation in the sensing layer of the device. This pH variation leads to change in potential at the ISFET's surface which is modeled by Bousse's equation. The potential variation is very less which gives low device sensitivity. By using dual gate, the sensitivity can be enhanced. The change in potential varies the threshold voltage of the device. thereby, varying the drain current, which can be measured. The simulated results of a fabricated CNT based dual gated ENFET is compared with the experimental results and found to be in good agreement.