Time-resolved near-field optics: exciton transport in semiconductor nanostructures

We present a systematic, temperature-dependent study of excitonic real-spac e transfer into single GaAs quantum wires using time-resolved low-temperatu re near-field luminescence spectroscopy. Excitons generated by local short pulse optical excitation in a 250nm spot undergo diffusive transport over a length of several micrometres and are subsequently trapped into the quantu m wire by optical phonon emission. The effect of local energy barriers in t he vicinity of the quantum wire on the real-space transfer dynamics is moni tored directly by mapping the time-resolved quantum wire luminescence, Expe riments at variable temperatures are compared to numerical simulations base d on drift-diffusive model calculations. and the spatio-temporal evolution of the two-dimensional exciton distribution within the nanostructure is vis ualized.