Ultrasensitive in situ label-free DNA detection using a GaN nanowire-based extended-gate field-effect-transistor sensor.

In this study, we have successfully demonstrated that a GaN nanowire (GaNNW) based extended-gate field-effect-transistor (EGFET) biosensor is capable of specific DNA sequence identification under label-free in situ conditions. Our approach shows excellent integration of the wide bandgap semiconducting nature of GaN, surface-sensitivity of the NW-structure, and high transducing performance of the EGFET-design. The simple sensor-architecture, by direct assembly of as-synthesized GaNNWs with a commercial FET device, can achieve an ultrahigh detection limit below attomolar level concentrations: about 3 orders of magnitude higher in resolution than that of other FET-based DNA-sensors. Comparative in situ studies on mismatches ("hotspot" mutations related to human p53 tumor-suppressor gene) and complementary targets reveal excellent selectivity and specificity of the sensor, even in the presence of noncomplementary DNA strands, suggesting the potential pragmatic application in complex clinical samples. In comparison with GaN thin film, NW-based EGFET exhibits excellent performance with about 2 orders higher sensitivity, over a wide detection range, 10(-19)-10(-6) M, reaching about a 6-orders lower detection limit. Investigations illustrate the unique and distinguished feature of nanomaterials. Detailed studies indicate a positive effect of energy band alignment at the biomaterials-semiconductor hybrid interface influencing the effective capacitance and carrier-mobility of the system.