A dielectric-modulated field-effect transistor for biosensing

Interest in biosensors based on field-effect transistors (FETs), where an electrically operated gate controls the flow of charge through a semiconducting channel, is driven by the prospect of integrating biodetection capabilities into existing semiconductor technology1. In a number of proposed FET biosensors, surface interactions with biomolecules in solution affect the operation of the gate or the channel2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19. However, these devices often have limited sensitivity. We show here that a FET biosensor with a vertical gap is sensitive to the specific binding of streptavidin to biotin. The binding of the streptavidin changes the dielectric constant (and capacitance) of the gate, resulting in a large shift in the threshold voltage for operating the FET. The vertical gap is fabricated using simple thin-film deposition and wet-etching techniques. This may be an advantage over planar nanogap FETs, which require lithographic processing20,21,22,23,24. We believe that the dielectric-modulated FET (DMFET) provides a useful approach towards biomolecular detection that could be extended to a number of other systems.