Light effects in asymmetric vertically coupled InAs/GaAs quantum dots

In this paper, the dependence of circular light polarization on the size asymmetry of self-assembled coupled quantum dots (SACQDs) has been studied. The heterostructure consists of ellipsoidal shaped QDs made with InAs which are embedded in a wetting layer and are surrounded by GaAs. By considering fully spin-polarized carriers within the QD structure, the light polarization has been estimated along the plane of spin polarized electrons (or holes). Circularly polarized light strongly depends on the ratio related to the different QD volumes. In the case of elongated QDs, small interdot distance and large volume ratio, the light polarization observed along the plane (110) receives the largest value (∼90%). On the other hand, the polarization efficiency of the emitted light decreases as the QD elongation decreases and finally vanishes for axially symmetric QD caps.