Vertical GaAs/AlGaAs heterostructure nanowires (NWs) with pure zinc blende structure were grown on Si (111) substrates by using AlGaAs/GaAs buffer layers. Axial and radial heterostructure NWs with different facets can be realized by tuning the growth temperature, so quantum wells with a triangular cross section enclosed by two {112}and one {110} facets can be obtained. Intensity of the room temperature photoluminescence can be greatly enhanced by passivating the surface states of GaAs NWs via growth of higher band-gap AlGaAs shells. The relevant growth mechanism is discussed. (C) 2012 Elsevier B.V. All rights reserved.