Simulation of Si nanowire biosensor: Effects of surface and biasing on sensitivity and linearity

We present here a numerically simulated pH sensing performance of Si nanowire (SiNW) FETs. The simulation is formulated based on Fermi-Dirac, Poisson-Boltzman, site-binding and Gouy-Chapman-Stern theories. Device characteristics (Vt, SS, On/Off, etc.) and pH sensing linearity/sensitivity from simulation match well with our sensing experiments using SiNW FETs fabricated with CMOS compatible process. Our study quantitatively shows the biasing under strong inversion yields better linearity, while sub-threshold yields better sensitivity. We also show that high sensitivity and linearity would require oxide surface with high density of reactive groups and good SAMs coverage.