Temperature dependence of the photoluminescence of InGaAs/GaAs quantum dot structures without wetting layer

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We analyze the photoluminescence temperature behavior of InGaAs/GaAs quantum dots grown by heterogeneous droplet epitaxy. Morphologically, these dots are nanocrystal InGaAs inclusions in the GaAs matrix, with a concave disk shape and, more important, no wetting layer is connecting the dots. The photoluminescence of the dots does not show any of the typical of the Stranski–Krastanov dots temperature properties, such as sigmoidal peak energy position and linewidth narrowing. We demonstrate that such behavior stems from the lacking of the thermally activated dot–dot coupling channel provided by the wetting layer thus preventing the establishment of a common quasiequilibrium in the whole dot ensemble.