We have studied the growth of doped InAsyP1-y (InAsP) NWs and InAsP-InP core-shell NWs. Using hydrogen chloride (HCl) we were able to prevent radial growth on the InAsP NWs. Undoped and H2S-doped InAsP NWs had almost pure wurtzite crystal structure, while DEZn-doped NWs showed wurtzite periodically separated by short sections of pure zincblende with rotational twins. Electrical measurements confirmed that the H2S-doped and DEZn-doped NWs were highly n- and p-doped, respectively. The core crystal structure strongly influenced the subsequent radial growth of InP shells, and we observed perfectly smooth shells on H2S-doped cores while the zincblende sections resulted in large bulges on the DEZn-doped cores. The average radial growth rate was more than twice as high on the DEZn-doped cores as on the H2S-doped cores. We found that the radial shell growth decreased at increasing temperature, while the axial growth increased. These results demonstrate the importance of the NW core crystal structure for the growth of core-shell NWs. (C) 2011 Elsevier B.V. All rights reserved.