Long wavelength vertically stacked InAs/GaAs(001) quantum dots with a bimodal size distribution: Optical properties and electronic coupling

Abstract

A molecular beam epitaxy (MBE) grown vertically stacked InAs/GaAs(001) quantum dots (QDs) structure emitting at 1.3 μm at room temperature has been investigated by photoluminescence (PL) experiment. The PL measurement has shown the coexistence of bimodal size distribution in the QD ensemble. Furthermore, the large size QDs are found to exhibit an interlayer vertical coupling in addition to a lateral coupling with neighboring small size QDs. A sigmoidal temperature dependence of the large size QD family’s PL peak as well as an anomalous decrease of the corresponding PL line width at intermediate temperature range are shown to occur. This behavior has been interpreted in terms of in-plane carrier transfer and repopulation process facilitated by the intermediate small size QDs states. These results can help to improve understanding some fundamental properties of long wavelength vertically stacked InAs/GaAs QDs.