  Most III-V semiconductors, which acquire the zinc-blende phase as bulk
materials, adopt the metastable wurtzite phase when grown in the form of
nanowires. These are new semiconductors with new optical properties, in
particular, a different electronic band gap when compared with that grown in
the zinc-blende phase. The electronic gap of wurtzite InAs at the Gamma-point
of the Brillouin zone (E0 gap) has been recently measured, E0 = 0.46 eV at low
temperature. The electronic gap at the A point of the Brillouin zone
(equivalent to the L point in the zinc-blende structure, E1) has also been
obtained recently based on a resonant Raman scattering experiment. In this
work, we calculate the band structure of InAs in the zinc-blende and wurtzite
phases, using the full potential linearized augmented plane wave method,
including spin-orbit interaction. The electronic band gap has been improved
through the modified Becke-Johnson exchange-correlation potential. Both the E0
and E1 gaps agree very well with the experiment. From the calculations, a
crystal field splitting of 0.122 eV and a spin-orbit splitting of 0.312 eV (the
experimental value in zinc-blende InAs is 0.4 eV) has been obtained. Finally,
we calculate the dielectric function of InAs in both the zinc-blende and
wurtzite phases and a comparative discussion is given.
