EXCITON INTERACTION EFFECTS IN THE EMISSION-SPECTRA OF SINGLE FREESTANDING INGAAS GAAS QUANTUM DOTS/

We report on highly spatially resolved photoluminescence studies on in dividual free-standing InGaAs/GaAs quantum dots with diameters between 100 and 40 nm. Single dots with spacings of 20 mu m between adjacent structures have been developed by low-voltage electron-beam lithograph y and wet chemical etching. Photoluminescence spectra taken at low exc itation densities systematically shift to higher energies with decreas ing dot diameter. With increasing excitation power, the emission inclu des additional peaks at higher energies due to transitions between the second and third quantized levels. Simultaneously, a renormalization of the transition energies by up to 2 meV and a significant broadening of the spectra are observed. The energy renormalization and spectral broadening are discussed on the basis of Coulomb interaction between e xcitons inside the dot and carrier pairs in the surrounding GaAs barri ers.