Page 1 of 28 Defect-Free Axial GaAs/GaAsP Nanowire Quantum Dots with Strong Carrier Confinement Yunyan Zhang, 1* Anton V. Velichko, 2 H. Aruni Fonseka, 3 Patrick Parkinson, 4 George Davis, 2 James A. Gott, 3 Martin Aagesen, 5 Suguo Huo, 6 Giorgos Boras, 1 Ana M. Sanchez, 3 David Mowbray 2 and Huiyun Liu 1* *E-mail: yunyang.zhang.11@ucl.ac.uk; huiyun.liu@ucl.ac.uk 1 Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom; 2 Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom 3 Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom 4 School Department of Physics and Astronomy and the Photon Science Institute, University of Manchester, M13 9PL, United Kingdom 5 Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark 6 London Centre for Nanotechnology, University College London, London WC1H 0AH, United Kingdom Abstract: Defect-free axial quantum dots (QDs) in self-catalysed nanowires (NWs) offer superior compatibility with Si technology and a high degree of structural controllability. However, there has been relatively little optimisation of their structural properties for operation at high temperatures and with long-term stability, particularly in terms of