Controlled charging of the same single quantum dot from +6e to -8e: Emission, shell filling and configuration interactions

We present photoluminescence spectra from single InAs/GaAs quantum dots embedded in a Schottky diode heterostructure. The pronounced Coulomb blockade can be exploited to change the exciton charge in discrete steps from +6e to -8e via an applied gate voltage. The results demonstrate a number of effects. The spectra of highly negatively charged excitons are dominated by configuration interactions in the final state, a viewpoint supported by few-electron calculations based on a harmonic oscillator potential. The positively charged excitons on the other hand show a very different behavior that can only be explained by taking strong spin-orbit coupling for the holes into account. Particularly, a hole charging sequence is revealed that defies Hund's rule as well as the Aufbau principle. Finally, photoluminescence from excited states offers direct access to the hole quantization energy. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.