Dielectric-Modulated Field Effect Transistors for DNA Detection: Impact of DNA Orientation

In this letter, we present a study that highlights the importance of electrostatic effects on DNA sequence orientation, and the subsequent influence on the functioning principles of nanogap embedded dielectric-modulated field effect transistor (DMFET) biosensors. We find that the orientation of DNA molecules is responsible for governing the sensitivity and dominance of charge or dielectric constant effect in nanogap embedded FET devices. Using 2-D TCAD simulations, the study not only provides a correct explanation for the observed trend of threshold voltage shifts for DNA detection using n-channel DMFET, which has been loosely attributed to the dominance of the charge effect, but also gives insight into the reason of higher sensitivity of p-channel over n-channel DMFET biosensors.