Impact-ionization field-effect-transistor based biosensors for ultra-sensitive detection of biomolecules

Deblina Sarkar, Harald Gossner, Walter Hansch, and Kaustav Banerjee


The phenomenon of impact-ionization is proposed to be leveraged for a novel biosensor design scheme for highly efficient electrical detection of biological species. Apart from self-consistent numerical simulations, an analytical formalism is also presented to provide physical insight into the working mechanism and performance of the proposed sensor. It is shown that using the impact-ionization field-effect-transistor (IFET) based biosensor, it is possible to obtain an increase in sensitivity of around 4 orders of magnitude at low biomolecule concentration and around 6 orders of magnitude at high biomolecule concentration compared to that in conventional FET (CFET) biosensors. Moreover, IFET biosensors can lead to significant reduction (around 2 orders of magnitude) in response time compared to CFET biosensors.

Biosensors are indispensable for modern society due to their wide applications in public healthcare, national and homeland security, forensic industries, and environmental protection. Currently, enzyme-linked immunosorbent assay (ELISA) based on optical sensing technology is widely used as a medical diagnostic tool as well as a quality-control check in various industries. For ELISA the labeling of biomolecules is needed, which requires the use of bulky, expensive optical instruments and hence is not suitable for fast point of care clinical applications. On the other hand, the biosensors based on field-effect-transistors (FETs)1–4 are highly attractive as they promise real-time label-free electrical detection, scalability, inexpensive mass production, and possibility of on-chip integration of both sensor and measurement systems. In a FET biosensor the function of the gate is carried out by the charged biomolecules that are captured by the specific receptors with which the gate dielectric is functionalized. However, there exists fundamental limitations on the sensitivity and response time of conventional FET (CFET) based biosensors.5–7 Here, we show that the phenomenon of impact-ionization8–10 can be leveraged to beat these limits, thereby leading to an ultra-sensitive and fast electrical biosensor.

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