Abstract
We investigate the polarization of excitonic transitions of single dispersed GaN nanowires with a diameter of about 50 nm. We observe donor-bound exciton transitions with a linewidth narrower than 250 μeV at 10 K, whereas the luminescence from free excitons exhibits a width of up to 5 meV. This broadening is larger than that observed for free excitons in the as-grown nanowire ensemble and is the result of inhomogeneous strain introduced by the nanowire dispersion. This strain lowers the symmetry of the lattice structure and allows A excitons to emit light polarized parallel to the nanowire axis. The polarization anisotropy of A excitons, however, is found to largely vary from one nanowire to another. In addition, the various bound-exciton lines in a given nanowire do not show the same polarization anisotropies. These findings can be explained by the dielectric contrast between the nanowire and its environment, but only when taking into account the strong variations of the dielectric function of GaN at the near band-edge.
Highlights
27 March 2015This strain lowers the the work, journal citation symmetry of the lattice structure and allows A excitons to emit light polarized parallel to the nanowire and DOI
The luminescence of semiconductor nanowires and its polarization is a topic of great current interest
We study the polarization of the excitonic transitions of single GaN nanowires with an average diameter of 50 nm using polarization-resolved micro-photoluminescence spectroscopy
Summary
This strain lowers the the work, journal citation symmetry of the lattice structure and allows A excitons to emit light polarized parallel to the nanowire and DOI. The various bound-exciton lines in a given nanowire do not show the same polarization anisotropies. These findings can be explained by the dielectric contrast between the nanowire and its environment, but only when taking into account the strong variations of the dielectric function of GaN at the near band-edge
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