  The separation of hot carriers in semiconductors is of interest for
applications such as thermovoltaic photodetection and third-generation
photovoltaics. Semiconductor nanowires offer several potential advantages for
effective hot-carrier separation such as: a high degree of control and
flexibility in heterostructure-based band engineering, increased hot-carrier
temperatures compared to bulk, and a geometry well suited for local control of
light absorption. Indeed, InAs nanowires with a short InP energy barrier have
been observed to produce electric power under global illumination, with an
open-circuit voltage exceeding the Shockley-Queisser limit. To understand this
behaviour in more detail, it is necessary to maintain control over the precise
location of electron-hole pair-generation in the nanowire. In this work we
perform electron-beam induced current measurements with high spatial
resolution, and demonstrate the role of the InP barrier in extracting energetic
electrons. We interprete the results in terms of hot-carrier separation, and
extract estimates of the hot carrier mean free path.
