Near-field spectroscopy of a coupled wire-dot nanostructure grown on (311)A GaAs

We discuss a detailed near-field spectroscopic study of the nanoscopic optical properties of a novel coupled wire-dot nanostructure grown on (311)A GaAs substrates. Photoluminescence spectra recorded with 150 nm spatial and 100 μeV spectral resolution permit mapping of two-dimensional variations of the lateral confinement potential and give direct information about growth dynamics. The absence of potential energy barriers between wire and dot makes these dots interesting optical markers for exciton diffusion via quantum well and wire states. The experiments indictate that exciton localization limits both the quasi-two and quasi-one-dimensional mobilities at low temperatures. The statistical parameters of the disorder potential underlying exciton localization, namely its correlation length and disorder amplitude are extracted by means of a novel statistical analysis of the two-energy autocorrelation function of ensembles of near-field PL spectra.