Agradecimentos: This work was financially supported by the Brazilian agencies FAPESP (grants 2013/02300-1, 2016/16365-6, 2011/50975-2, 2012/22617-7 and 2015/16611-4) and CNPq (grants 479486/2012-3, 475343/2013-1 and 305769/20154) as well as the Spanish Ministry of Science and Innovation (grant MAT2009-10350). D S Oliveira and P K Sahoo acknowledge FAPESP for funding their scholarships. A. Molina-Sanchez acknowledges the Luxembourg National Research Fund, project C14/MS/7731521, FAST-2DMAT. The authors also acknowledge the National Laboratory of Nanotechnology (LNNANO/CNPEM, Brazil) for granting access to electron microscopy facilities Ver menos

Abstract: InAs nanowires grown by vapor-liquid-solid (VLS) method are investigated by photoluminescence. We observe that the Fermi energy of all samples is reduced by similar to 20 meV when the size of the Au nanoparticle used for catalysis is increased from 5 to 20 nm. Additional capping with a thin InP shell enhances the optical emission and does not affect the Fermi energy. The unexpected behavior of the Fermi energy is attributed to the differences in the residual donor (likely carbon) incorporation in the axial (low) and lateral (high incorporation) growth in the VLS and vapor-solid (VS) methods, respectively. The different impurity incorporation rate in these two regions leads to a core/shell InAs homostructure. In this case, the minority carriers (holes) diffuse to the core due to the built-in electric field created by the radial impurity distribution. As a result, the optical emission is dominated by the core region rather than by the more heavily doped InAs shell. Thus, the photoluminescence spectra and the Fermi energy become sensitive to the core diameter. These results are corroborated by a theoretical model using a self-consistent method to calculate the radial carrier distribution and Fermi energy for distinct diameters of Au nanoparticles Ver menos