NSTI Nanotech 2009

InN nanowire based transistors and sensors

G. Koley, Z. Cai
University of South Carolina, US

Keywords: InN nanowires, high quality, coplanar, high mobility, indium oxide shell layer, gas sensing


High quality InN nanowires (NWs) were grown from nanoscale catalyst patterns by vapor-liquid-solid mechanism on SiO2/Si substrates. The co-planar nanowires bent spontaneously or deflected from other nanowires at multiples of 30 forming nano-networks as well as barrier guided growth. The NW diameters were found to vary from 15 80 nm, while their length varied from 5 20 m. Smooth and planar NWs used to fabricate field effect transistors (FET), in a back-gated geometry, exhibited excellent drain current modulation as well as drain current saturation. The best mobility obtained for these NWs is 1108 cm2/Vs, while the carrier concentration is 1.41018 cm-3, which is much improved compared to prior results on InN NWs and most other semiconducting NWs. The mobility varied quite dramatically with diameter, which has been observed before for InN NWs, and is possibly influenced by the presence of surface oxide in some NWs. The NW FET demonstrated high sensitivity to trace NO2 when a thin In2O3 shell layer was present around the InN core. The adsorption of the NO2 molecules reduced the density of carriers confined at the InN/In2O3 interface, reducing the drain current. The best sensitivity obtained for trace NO2 was 45 ppb in ambient conditions.
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