  We use polarized photocurrent spectroscopy in a nanowire device to
investigate the band structure of hexagonal Wurtzite InAs. Signatures of
optical transitions between four valence bands and two conduction bands are
observed which are consistent with the symmetries expected from group theory.
The ground state transition energy identified from photocurrent spectra is seen
to be consistent with photoluminescence emitted from a cluster of nanowires
from the same growth substrate. From the energies of the observed bands we
determine the spin orbit and crystal field energies in Wurtzite InAs. This
information is essential to the development of crystal phase engineering of
this important III-V semiconductor.
