Analytical modeling of underlap graded channel field effect transistor as a label-free biosensor

Abstract

Biosensor based on the field-effect transistor (FET) with an underlap region in one side of the gate has high sensitivity and high probability of biomolecules binding. However, the underlap region presence results in lesser gate control over the channel, leading to lower device characteristics control. In this paper, the channel's grading has been employed in FET with an underlap region in the middle of the gate for label-free biosensing application. Surface potential and threshold voltage models are proposed to analyze its effectiveness in sensing DNA and neutral biomolecules. The introduction of DNA in the underlap area causes hybridization, which changes the biosensor's electrical characteristics due to dielectric and charge modulation and is used as a sensing matrix. The results reveal that the proposed biosensor is not only highly sensitive but also yields improved circuit performance. The analytical findings are verified by using TCAD simulation data. This study helps in the design of a new label-free, ultra-small, and highly sensitive biosensor.