Abstract:
The current-voltage (I–V) characteristics of single nanowire (NW) Field
Effect Transistors are found to be depended on the device geometry and
contact resistances. The proposed electronic model for the metalsemiconductor-
metal structure of the device, which has two back-to-back
Schottky diodes connected in series with the NW resistor, is shown to be able
to extract Schottky barrier heights, mobility, conductivity and carrier denstiy
using only a few fitting variables. The thermionic emission and thermionic
field emission theories were used to model the current transport through the
metal-semiconductor junctions. The model was applied to fit a couple of
experimental I–V curves of Zincblende n-type InP NWs using Mathematica.
These InP NWs were ~100 nm in diameter and ~8 μm in length. The source
and drain electrodes of the fabricated device were defined by photolithography
followed by metal evaporation of Ti/Al.The normality of the data was verified
graphically and analytically using standard tests. The model fitting was
validated by graphical residual analysis and chi square test. The extracted
average carrier density and mobility of these NWs were ~2.00 x 1016 cm-3 and
~8471 cm2/(Vs) respectively. They are in good agreement with the mobilities
of doped III-V semiconductor NWs with similar carrier densities. It is
observed that the extracted barrier heights of the NW devices are (0.07 – 0.25)
eV in range which are in good agreement with their I-V curves. The
conductivity estimated for these NWs was ~2.70 x 103 Sm-1 and it agrees with
the conductivities of semiconductor NWs.
