Excitonic states in GaAs quantum dots fabricated by local droplet etching

The influence of dot size and shape on the excitonic structure of GaAs/AlGaAs quantum dots (QDs) is studied experimentally and theoretically. Almost strain-free GaAs QDs are fabricated by epitaxially filling of nanoholes in an AlGaAs surface. The nanoholes are formed in a self-assembling fashion by local droplet etching. As an important point, the size of the QDs can be adjusted by the hole filling level. As a consequence, the exciton recombination energy can be controllably varied over a range of 130 meV by the dot size. We present micro- and macro-photoluminescence measurements of the s-shell recombinations. With the hole shape determined using atomic force microscopy and the amount of GaAs filled into the holes, we have quite precise input parameters for a simulation of the excitonic states in the QDs. The measured exciton and biexciton recombination energies are well reproduced by calculations based on eight band k·p theory and configuration interaction scheme with a deviation of less than 7 meV.