Spatially resolved spectroscopy on single self-assembled quantum dots

We report about spatially resolved experiments on self-assembled InGaAs qua ntum dots. Single quantum dots can be investigated by using STM-induced lum inescence spectroscopy. The quantum dot occupancy can be increased via the STM tip current, which results in state filling and therefore in the onset of discrete excited state luminescence. In the limit of low injection curre nts, a single emission line from the ground state of the dot is observed. U sing near-field spectroscopy through shadow masks, we have investigated the optical properties of single self-assembled InGaAs quantum dots as a funct ion of occupancy and magnetic field. This allows us to fully resolve diamag netic/orbital effects, Zeeman splitting, and to determine manybody-correcti ons. Photoluminescence excitation spectra further reveal a strong contribut ion of phonon assisted processes in quantum dot absorption.