Spontaneous quantum dot formation at InxGa1-xAs/InyGa1-yAs interfaces

We have performed reflectivity and photoluminescence measurements on a set of InxGa1-xAs/InyGa1-yAs/GaAs(001) stepped/asymmetric quantum wells with an intentionally abrupt change of indium composition (x=0.149, y=0.064). These measurements have been compared against extensive spectroscopic data gathered on a set of symmetric quantum wells with similar structural parameters. For both symmetric and asymmetric quantum well samples, reflectivity spectra agree well with theoretical calculations both in terms of peak energy positions and line shapes. The photoluminescence spectra from the asymmetric quantum well samples are consistent with the hypothesis of three-dimensional exciton confinement induced by local and random potential fluctuations at the In-alloy/In-alloy interface. A brief examination of the possible formation mechanisms leading to the formation of such ‘natural quantum dots’ at this poorly studied interface will be presented.