  Understanding of the electrical contact properties of semiconductor nanowire
(NW) field effect transistors (FETs) plays a crucial role in employing
semiconducting NWs as building blocks for future nanoelectronic devices and in
the study of fundamental physics problems. Here, we report on a study of the
contact properties of Ti/Au, a widely used contact metal combination, to
individual InSb NWs via both two-probe and four-probe transport measurements.
We show that a Schottky barrier of height $\Phi_{\rm{SB}}\sim20\ \rm{meV}$ is
present at the metal-InSb NW interfaces and its effective height is gate
tunable. The contact resistance ($R_{\rm{c}}$) in the InSb NWFETs is also
analyzed by magnetotransport measurements at low temperatures. It is found that
$R_{\rm{c}}$ at on-state exhibits a pronounced magnetic field dependent
feature, namely it is increased strongly with increasing magnetic field after
an onset field $B_{\rm{c}}$. A qualitative picture that takes into account
magnetic depopulation of subbands in the NWs is provided to explain the
observation. Our results provide a solid experimental evidence for the presence
of a Schottky barrier at Ti/Au-InSb NW interfaces and can be used as a basis
for design and fabrication of novel InSb NW based nanoelectronic devices and
quantum devices.
