Different growth mechanisms of bimodal InAs/GaAs QDs

In this work, we have adopted photoluminescence (PL) to study the evolution of self-assembled InAs/GaAs quantum dots (QDs) as a function of InAs deposition amount. With increasing InAs amount, the QDs transfer from unimodal to bimodal size distribution. Moreover, the PL peak of small-size QDs gradually deviates from the well-known anomalous temperature dependency of QDs, and follows the InAs intrinsic bandgap redshift at large deposition amount, whereas the PL peak of large-size QDs demonstrates the anomalous temperature dependency within the investigated deposition range. This indicates the small-size QDs are progressively detached from WL. The observations are interpreted with respect to different growth mechanisms of the two QDs families: the large-size QDs locate on the terraces and expand their sizes at the expense of the floating indium atoms, and the small-size QDs are at the step edges and grow by eroding WL.