Temperature-Dependent Photoluminescence in CdTe/ZnTe Triple Quantum Dots

We studied the optical properties of CdTe/ZnTe quantum dots (QDs) in single, double, and triple QD structures by measuring the temperature-dependent photoluminescence (PL). On going from the single to the triple QD structures, the PL peak position of the QDs was blue shifted. This blue-shift was attributed to compressive strain imparted by the separation layers and to material intermixing. Temperature-dependent PL measurements of the triple QD structures showed that, as the temperature increased, the PL peak intensity for the 4.5-monolayer (ML) QDs decreased less than it did for the 3.0- and the 3.5-ML QDs. The activation energy of the 4.5-ML QDs in the triple QD structures was larger than that of the corresponding 4.5-ML QDs in the single QD structures. The reason for this is that, as the temperature increases, some carriers disappear due to non-radiative recombination, but many carriers in the 3.0- and the 3.5-ML QDs move to the 4.5-ML QDs in the triple QD structures, and those carriers then undergo radiative recombination.