The impact of different channel doping concentrations on the performance of polycrystalline silicon nanowire field-effect transistor biosensor

Abstract

This paper investigates the effect of different doping concentrations on the performance of a polycrystalline silicon nanowire (poly-SiNW) field-effect transistor (FET) for biosensing application. The p-type poly-SiNW FET biosensor was designed and simulated in a commercial numerical simulation, Silvaco ATLAS. Three different p-type doping concentrations (i.e. 0.5×1018, 1×1018, and 5×1018 cm−3) were applied to the channel of the designed biosensor in order to observe their substantial impact on the device electrical characteristic through the simulation process. The doping concentration was indirectly proportional to the electrical resistivity, ρ of the poly-SiNW channel. Therefore, the reduction of doping concentration had caused the nanowire to exhibit higher electrical resistance, R. Furthermore, the biosensor performance during detection was investigated through the application of several negatively interface charge densities, QF (i.e. −0.1×1012, −0.5×1012, and −1×1012 cm−2) on the surface of the poly-SiNW channel, to imitate the availability of negatively charged target deoxyribonucleic acid (DNAs) captured on the surface of the biosensor. The increase of negatively QF on the channel region of the poly-SiNW had caused accumulation of hole conduction channel beneath the poly-SiNW surface, hence allowed more drain current, ID to flow from drain to source region. The changes in ID values due to the applied QF that represent the different concentrations of captured target DNA by the biosensor were used to calculate the sensitivity and limit of detection (LOD) for the biosensor. Poly-SiNW biosensor with low doping concentration of 0.5×1018 cm−3 had demonstrated higher sensitivity of 0.29 μA/cm−2 with low LOD down to 8.28×1010 cm−2, and therefore can be considered to be utilized in the actual fabrication of the poly-SiNW FET biosensor.