Sensitivity Investigation of Backgated Silicon Nanowire Biosensors for Liquid Gatting

Abstract

We performed a feasibility study of tailoring sensitivity of Si nanowire through backgate bias arrangement for various NW length and thickness. Three different thicknesses of 100 nm, 50 nm and 25 nm were chosen and each thickness consisted of 5 different channel lengths - 1000 nm, 750 nm, 500 nm, 250 nm and 100 nm respectively. It can be seen that the backgate bias has a big influence on the sensitivity of a p-type SiNW. A backgate bias leading to a depletion of the NW body increases the sensitivity whereas the backgate bias leading to an accumulation of significant carriers decreases the sensitivity of NW. For a fixed NW thickness, a decrease of NW length found to degrade sub-threshold slope and hence NW sensitivity. But for a fixed NW length a decrease of NW thickness improves the sub-threshold characteristics and sensitivity. When the NW thickness is 100 nm a peak sensitivity of 2390%/v is found for 1um long NW which degrades to a value of 349%/V at 100nm length. However, 100 nm long NW’s sensitivity can be improved by reducing NW thickness and adjusting backgate bias. A 100 nm long 25 nm thick NW exhibits an improved sensitivity of 2730%/V with +7V of backgate bias. This result implies that with appropriate backgate bias arrangement, low doped then NW can be used for single molecule detection as biosensors. Our simulation revealed that a 25 nm thick 1 um long NW with +7V of backgate bias gives a sensitivity of 3050 %/V.