Nanowire-based structures for infrared to ultraviolet emitters studied by cathodoluminescence.

Nanowires are structures with features on the nanoscale, and it is therefore essential to study their properties on that scale. We present optical data from a variety of nanowire-based structures using cathodoluminescence imaging and spectroscopy. One important feature of nanowires is the stacking sequence of the crystal, either zincblede, wurtzite or a mix of the two. We show that this has an impact on the optical properties. In radial quantum wells, the thickness can be controlled on a monolayer level, in the case of flat side facets of the nanowires. With rough side facets, the quantum well collapses into quantum dots, as revealed by cathodoluminescence imaging. In order to extend the emission wavelength of light-emitting diodes into the ultraviolet or to cover the whole visible range, we use nanowire-seeded truncated pyramids as bases for these devices, based on either GaInN (visible) and AlGaN (ultraviolet).