Photoluminescence and time-resolved photoluminescence characteristics of InxGa(1−x)As/GaAs self-organized single- and multiple-layer quantum dot laser structures

The characteristics of ground and excited state luminescent transitions in ${\mathrm{In}}_{\mathrm{0.4}}{\mathrm{Ga}}_{\mathrm{0.6}}\mathrm{As/GaAs}$ and ${\mathrm{In}}_{\mathrm{0.35}}{\mathrm{Ga}}_{\mathrm{0.65}}\mathrm{As/GaAs}$ self-organized single- and multiple-layer quantum dots forming the active regions of lasers have been studied as a function of incident excitation intensity, temperature and number of dot layers. The results have been correlated with molecular beam epitaxial growth conditions. The threshold excitation density for the saturation of the ground state increases with the number of dot layers and no saturation is observed in samples with more than six dot layers up to an excitation power density of $\text{2\hspace{0.17em}}{\mathrm{kW/cm}}^{\mathrm{2}}.$ The luminescent decay times for the ground and excited states are around 700 and 250 ps, respectively, almost independent of the number of dot layers.