We investigate the Raman intensity of EH2 phonons in wurtzite GaAs nanowire
ensembles as well as single nanowires as a function of excitation wavelength.
For nanowires with radii in the range of 25 nm, an almost complete quenching
of the EH2 phonon line is observed for excitation wavelengths larger than 600
nm. The observed behavior is quantitatively explained by the dielectric
polarization contrast for the coupling of light into the GaAs nanowires. Our
results define the limits of Raman spectroscopy for the detection of the
wurtzite phase in semiconductor nanowires
