Fabrication and characterization of axially doped silicon nanowire tunnel field-effect transistors.

Tunnel field-effect transistors were fabricated from axially doped silicon nanowire p-n junctions grown via the vapor-liquid-solid method. Following dry thermal oxidation to form a gate dielectric shell, the nanowires have a p-n-n(+) doping profile with an abrupt n-n(+) junction, which was revealed by scanning capacitance microscopy. The lightly doped n-segment can be inverted to p(+) by modulating the top gate bias, thus forming an abrupt gated p(+)-n(+) junction. A band-to-band tunneling current flows through the electrostatically doped p(+)-n(+) junction when it is reverse biased. Current-voltage measurements performed from 375 down to 4.2 K show two different regimes of tunneling current at high and low temperatures, indicating that there are both direct band-to-band and trap-assisted tunneling paths.

Disorder dominated microwave conductance spectra of doped silicon nanowire arrays.

Conductance spectra of doped silicon nanowire (SiNW) arrays were measured from 0.5 to 50 GHz at temperatures between 4 and 293 K. For arrays consisting of 11 to >10(4) SiNWs, the conductance was found to increase with frequency as f(s), with 0.25 < s < 0.45, consistent with behavior found universally in disordered systems. A possible cause is disorder from Si/SiO x interface states dominating the conductance due to the high surface-to-volume ratio of the nanowires.