Numerical simulation of different silicon nanowire field-effect transistor channel lengths for biosensing application

Abstract

This paper focuses on the impact towards the performance of silicon nanowire field-effect transistor (SiNW-FET) for biosensing application based on different channel lengths of the nanowire. A device numerical modelling tool, Silvaco ATLAS was used to design three p-type SiNW-FET biosensors with different lengths of 0.5, 1.0, and 10.0 μm. The designed devices were simulated in order to observe and compare the effect of different channel length towards the electrical characteristic of the devices. Increase of the nanowire channel length had caused reduction of drain current, ID flowed through the channel from drain to source region. This is related to the increase of electrical resistance, R of the nanowire with the increase of nanowire length, L. In a way to study the effect of different channel lengths on the performance of the SiNW-FET biosensor, several negatively interface charge densities, QF (i.e. −0.1×1012, −0.5×1012, and −1×l012 cm−2) were introduced on the surface of the SiNW channel to represent as the actual target deoxyribonucleic acid (DNA) captured by the bioreceptor of the biosensor. Based on the results, these negatively QF attracted the hole carriers below the surface of p-type nanowire to form an accumulation of charge carriers in the channel, causing an increase in the device output ID. Increase of the applied negative charge density had allowed for more ID to flow across the channel between drain and source region. The changes of ID with the applied QF are utilized to determine the sensitivities and limit of detections (LOD) for all designed biosensor with different channel lengths. In comparison, the smallest nanowire length of 0.5 μm produced the highest sensitivity and lowest LOD of 2.17 μA/cm−2 and 7.85×1010 cm−2, respectively, hence demonstrates better performance of SiNW-FET biosensor for the detection of specific charged DNA in analyte.