Surface
passivated InAs/InP core/shell nanowires
J W W van Tilburg, R E Algra, W
G G Immink, M Verheijen, E P A M Bakkers and L P Kouwenhoven
Semi conductor science and Technology
25, issue 2 (2009) 024011
Abstract:
We report the
growth and characterization of InAs nanowires capped with a 0.5–1 nm
epitaxial InP shell. The low-temperature field-effect mobility is
increased by a factor 2–5 compared to bare InAs nanowires. We extract
the highest low-temperature peak electron mobilities obtained for
nanowires to this date, exceeding 20 000 cm2 V s−1. The electron
density in the nanowires, determined at zero gate voltage, is reduced
by an order of magnitude compared to uncapped InAs nanowires. For
smaller diameter nanowires we find an increase in electron density,
which can be related to the presence of an accumulation layer at the
InAs/InP interface. However, compared to the surface accumulation layer
in uncapped InAs, this electron density is much reduced. We suggest
that the increase in the observed field-effect mobility can be
attributed to an increase of conduction through the inner part of the
nanowire and a reduction of the contribution of electrons from the
low-mobility accumulation layer. Furthermore the shell around the InAs
reduces the surface roughness scattering and ionized impurity
scattering in the nanowire.