Signal-to-noise ratio enhancement using the gate coupling effect

We investigated the transport properties of n+-p-n+ liquid-gated Si NW FET biosensors using noise spectroscopy. We found that the gate coupling effect results in the channel position being shifted into the depth of the nanowire when the back gate voltage is applied. It was shown that the noise level and signal-to-noise ratio depends on the selected operating mode. By applying the back gate voltage, the sensor characteristics can be optimized in both the linear and saturation regimes. Results demonstrate that interaction processes with the traps of the top dielectric layer can be considerably reduced. Using the back gate voltage, we obtained an improved signal-to-noise ratio (SNR) and thus a sensitivity enhancement of up to 100%. This value is twice as high as the value previously reported for p+-p-p+ structures