Zinc blende structure GaAs/AlGaAs core-multishell nanowires (NWs) are grown on a GaAs(111) B substrate by a two-temperature process using an Au-catalyzed vapor-liquid-solid mechanism and metal organic chemical vapor deposition, respectively. Defect-free radial heterostructure NWs are formed. It can be concluded that the NWs are grown with the main contributions from the direct impingement of the precursors onto the alloy droplets and little from adatom diffusion. The results indicate that the droplet acts as a catalyst rather than an adatom collector. The photoluminescence spectra reveal that the grown NWs have much higher optical efficiency than bare GaAs NWs.