We report resonant Raman scattering (RRS) by the TO, LO, and 2 LO modes of
single wurtzite and zinc-blende GaAs nanowires. The optical band gap of
wurtzite GaAs is 1.460eV ± 3meV at room temperature, and 35 ± 3meV larger than
the GaAs zinc-blende band gap. Raman measurements using incoming light
polarized parallel and perpendicular to the wire c axis allowed us to
investigate the splitting of heavy Γ9 and light-hole Γ7 band at the Γ point of
65 ± 6meV.