Operating and Sensing Mechanism of Electrolyte-Gated Transistors with Floating Gates: Building a Platform for Amplified Biodetection

Electrolyte-gated transistors (EGTs) with floating gates (FGs) are an emerging platform for label-free electronic biodetection. Advantages of floating gate EGTs (FG-EGTs) include signal amplification and inherent sensitivity to small voltages, on the order of 10 mV, associated with chemical binding events on the floating gate electrode surface. Here we examine how the performance of these devices depends on their architecture, specifically the relative sizes (areas) of the control gate, the floating gate, and the sourcesemiconductordrain channel. The results allow optimization of the geometry for future biodetection studies. Further, using self-assembled monolayer (SAM) chemistry, we also examine the effect of chemisorption on the floating gate on the current voltage (I-V) characteristics. We find the FG-EGTs respond to both interfacial dipoles and capacitance changes and that the I-V behavior can be reasonably predicted with a lumped capacitor model. Overall, this work provides the most detailed picture to date of the operating mechanism of these promising electronic sensing devices.