Effect of nanowire number, diameter, and doping density on nano-FET biosensor sensitivity

Semiconductive nanowire-based biosensors are capable of label-free detection of biological molecules. Nano-FET (field-effect transistor) biosensors exhibiting high sensitivities toward proteins, nucleic acids, and viruses have been demonstrated. Rational device design methodologies, particularly those based on theoretical predictions, were reported. However, few experimental studies have investigated the effect of nanowire diameter, doping density, and number on nano-FET sensitivity. In this study, we devised a fabrication process based on parallel approaches and nanomanipulation-based post-processing for constructing nano-FET biosensor devices with carefully controlled nanowire parameters (diameter, doping density, and number). We experimentally reveal the effect of these nanowire parameters on nano-FET biosensor sensitivity. The experimental findings quantitatively demonstrate that device sensitivity decreases with increasing number of nanowires (4 and 7 nanowire devices exhibited a ∼38 and ∼82% decrease in sensitivity as compared to a single-nanowire device), larger nanowire diameters (sensors with 81-100 and 101-120 nm nanowire diameters exhibited a ∼16 and ∼37% decrease in sensitivity compared to devices with nanowire diameters of 60-80 nm), and higher nanowire doping densities (∼69% decrease in sensitivity due to an increase in nanowire doping density from 10(17) to 10(19) atoms·cm(-3)). These results provide insight into the importance of controlling nanowire properties for maximizing sensitivity and minimizing performance variation across devices when designing and manufacturing nano-FET biosensors.