Self-assembled InGaAs quantum dot clusters with controlled spatial and spectral properties.

Planar quantum dot clusters (QDCs) consisting of six InGaAs quantum dots (QDs) formed around a GaAs nanomound are the most sophisticated self-assembled QDCs grown by molecular beam epitaxy thus far. We present the first photoluminescence measurements on individual hexa-QDCs with high spatial, spectral, and temporal resolution. In the best QDCs, the excitons confined in individual QDs are remarkably close in energy, exhibiting only a 10 meV spread. In addition, a biexponential decay profile and small variation in decay rates for different QDs was observed. The homogeneous energetics and dynamics suggest that the sizes, shapes, and composition of the QDs within these clusters are highly uniform.