Exciton interaction effects in the emission spectra of single free-standing InGaAs/GaAs quantum dots

Abstract

We report on highly spatially resolved photoluminescence studies on individual free-standing InGaAs/GaAs quantum dots with diameters between 100 and 40 nm. Single dots with spacings of 20 μm between adjacent structures have been developed by low-voltage electron-beam lithography and wet chemical etching. Photoluminescence spectra taken at low excitation densities systematically shift to higher energies with decreasing dot diameter. With increasing excitation power, the emission includes 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 excitons inside the dot and carrier pairs in the surrounding GaAs barriers.