Investigation on the non-linear behaviour of silicon nanowires and assessment of the biosensing potential

Abstract

We perform a rigorous study on the conduction characteristics of long, low doped and relatively thick p-type silicon nanowire (SiNW) with different bias polarities/strengths to find out the origin of the non-linear electrical characteristics and to find out the applicable bias window for ensuring the gate responsive operation as biosensor. Depending on the polarity and strength of the drain bias (VDS)/liquid gate voltage (VGS), conduction is found to be confined in the bulk, in the surface accumulation region or in a path that comprises both accumulation region and the bulk thereby results in the diode or transistor like non-linear output characteristics. Although the SiNW is long without any junctions in the source/drain, the transfer characteristics exhibits a distinct shift with the increase of VDS when VDS is positive. The non-linear characteristics of SiNW is analysed to extract the gate responsive biasing window and it is found that the positive VDS application provides the flexibility of choosing diverse range of VDS and VGS voltages. As such, the shift in the transfer characteristic which is not appreciated for logic operation appears to be beneficiary for nanowire biosensors. This study sheds light on the variable electrical characteristics of SiNW reported in the literature and shows the way to choose appropriate bias conditions for biosensing applications.