Double-gate suspended silicon nanowire transistors with tunable threshold voltage for chemical/biological sensing applications

A double-gate suspended silicon nanowire transistor (DGSSiNWT) is proposed for conduction-based chemical/biological sensing applications. The doping profile is uniform across the device without any junction. The suspended silicon nanowire (SiNW) provides a larger surface area that can be used to enhance the sensitivity. Two side gates, which work as the main gate and tuning gate, are separated from the SiNW by air gap and control the electrical conduction of the suspended structure. Using the tuning gate, we have optimized the operating point of device to achieve the highest sensitivity. The sensitivity, defined as the ratio of threshold voltage shift to tuning gate voltage variation, is observed to be up to 6.5. The estimated charge sensitivity of our devices is at least 20 times higher than the reported value for non-suspended SiNW transistors.