Dielectric Modulated Bilayer Electrode Top Contact OTFT for Label Free Biosensing
Sushil Kumar Jain, Amit M. Joshi, Linga Reddy Cenkeramaddi
Abstract
In this paper, dielectric modulated bilayer electrodes top contact organic field effect transistor (DMBETC-OTFT) is investigated as a biosensing device for label-free detection of biomolecules. The nanocavity used for biomolecule detection is created by etching the oxide in a conventional OTFT device. Neutral and charged biomolecules can be detected by the proposed device using their respective dielectric constants and charge densities. Subthreshold swing (SS), on-current ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I<sub>ON</sub></i> ), and on-off current ratio ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I<sub>ON</sub>/I<sub>OFF</sub></i> ) are the main biosensing performance characteristics computed and compared for different gate work function (ϕ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>m</i></sub> ) and cavity thickness ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T<sub>gap</sub></i> ) for the proposed biosensor device. The change in drain current ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I<sub>D</sub></i> ), as well as the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I<sub>ON</sub>/I<sub>OFF</sub></i> ratio, have both been calculated to investigate the sensitivity of the proposed biosensor. The influence of the gate work function is also investigated to improve the sensitivity of the proposed device. According to the finding of this study, using a gate work function with a lower value results in a significant increase in sensitivity. For charged biomolecules ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q<sub>f</sub></i> = +1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cm</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">–2</sup> ) with dielectric constant of biomoecules (K = 12), the highest drain current sensitivity is 4.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The drain current sensitivity achieved is four times greater, when comparing the proposed device to the latest published work of metal controlled dielectric modulated OTFT-based sensor. The proposed device also has a high <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I<sub>ON</sub>/I<sub>OFF</sub></i> sensitivity of 4.60 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> when <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V<sub>GS</sub></i> = -3.0 V and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V<sub>DS</sub></i> = -1.5 V. In light of its high sensitivity, low cost, and bio-compatibility, the DMBETC-OTFT biosensor holds great promise for the advancement of new demanding flexible biosensing applications.