We report micro Raman scattering spectra from free-standing Au-catalyzed self-assembled GaAs nanowires on (111) B GaAs grown by metalorganic vapor phase epitaxy. The nanowires are [111] B aligned and kink-free. Their base diameter distribution is narrow (11.4 nm standard deviation) and closely matches the size (60 nm) of the Au nanoparticles at their tip. Depending on the exciting laser power density (several hundred μW/μm^ 2) the Raman spectra of the nanowires show thermally induced frequency shifts and broadening of the Raman lines. Series of power dependent spectra allow to extrapolate the phonon line shape and frequency free from thermal effects. The two main Raman lines corresponding to TO and LO of the bulk do not show frequency shifts with respect to the bulk. However, the Raman spectra exhibit new vibrational modes appearing in the gap between the TO and LO phonon lines. The …