DNA detection with top-down fabricated silicon nanowire transistor arrays in linear operation regime (Phys. Status Solidi A 6∕2016)

Silicon nanowire field-effect transistors (SiNW-FETs) were fabricated in a top-down process on wafer-scale. They can be regarded as nano-sized, long-channel, ion-sensitive fieldeffect transistor devices (ISFETs) and are offering a label-free sensing of DNA molecules based on the detection of the biomolecules' charges. In the work by Miriam Schwartz et al. (see pp. 1510-1519 ) SiNW arrays were site-specifically modified by DNA capture sequences using a microspotter and hybridization with complementary target DNA was recorded. The authors show that the electronic characteristics of the SiNW-FETs can be fitted by an advanced MOSFET model taking narrow channel effects into account. From these experiments, the immobilization of the DNA to the wire structure is leading to two effects: first, the threshold voltage is changing leading to a shift in the transistors' transfer characteristics similar to what was described before for ISFET devices. In addition, upon DNA binding, a general increase in charge carrier density inside the nanowire is leading to an enhanced conductance. Schwartz et al. suggest that the latter effect is scaling with nanowire dimensions, while the surface effect is typically constant for all sensor structures.