Directional emission from leaky and guided modes in GaAs nanowires measured by cathodoluminescence

8 págs.; 4 figs.We measure the polarization-resolved angular emission distribution from thin and thick GaAs nanowires (diameters ∼110 and ∼180 nm) with cathodoluminescence polarimetry. The nanowires, which horizontally rest on a thin carbon film, are excited by a 5 keV electron beam and emit band gap luminescence at a central wavelength of 870 nm. The emission can couple to different waveguide modes that propagate along the wire, are dependent on the wire diameter, and determine the directionality and polarization of the emission. Although each measured nanowire can support different modes, the polarized emission is dominated by the TM01 waveguide mode in all cases, independently of wire diameter. When exciting the nanowires close to the end facets, the thin and thick wires exhibit opposite directional emission. The emission from thin nanowires is dominated by a leaky TM01 mode that leads to emission toward the opposite end facet (emission to the right when exciting the left-side edge). For the thick wires, however, the TM01 mode is guided but also lossy due to absorption in the substrate. In such a case, the wires emit toward the excited end facet (to the left when exciting the left-side edge). The emission directionality switches for nanowire diameters in the range of 145-170 nm. We show that the measurements agree well with both a simple 1D current model and numerical simulations. The high spatial resolution of angle- and polarization-resolved cathodoluminescence spectroscopy provides detailed insight into the nanoscale emission and propagation of light in semiconductor nanowires. Copyright © 2016 American Chemical SocietyThis work is part of the Stichting voor Fundamenteel Onderzoek der Materie (FOM) as well as the Dutch Technology Foundation STW, which are financially supported by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) and the Dutch Ministry of Economic Affairs. It is also part of NanoNextNL, a nanotechnology program funded by the Dutch Ministry of Economic Affairs, part of an industrial partnership program between Philips and FOM, and is supported by the European Research Council (ERC). The Spanish Ministerio de Economıía y Competitividad is also acknowledged for financial support through the grants NANOPLAS+ (FIS2012-31070) and LENSBEAM (FIS2015- 69295-C3-2-P).Peer Reviewe