An explanation for the non-monotonic temperature dependence of the photoluminescence spectral features of self-organized InAs QDs
Résumé
Temperature-dependent photoluminescence (PL) measurements under different excitation densities were performed on self-assembled InAs quantum dots (QDs) grown by molecular beam epitaxy. Non-monotonic evolutions in the curves of the PL spectral parameters as a function of the sample temperature were observed in the low-temperature regime. Indeed, the PL peak energy of the QDs shows a sigmoidal variation with increasing temperature. This component is accompanied by an anomalous increase in the integrated intensity over the temperature range of 8–50K. These behaviors have been attributed to the optical emission from deep states that exist in the potential of the dots. A simple rate equation model, which describes the thermally activated emission and trapping of photo-injected carriers, is proposed to illustrate the interpretations made regarding the evolution of the integrated PL intensity with increasing temperature. A good agreement between the model simulation and the PL data was obtained for temperatures ranging from 8 to 300K. It was found that the thermally activated process of the intra-dot redistribution of carriers provides a good description of the anomalous behaviors encountered in the PL investigations depending on the temperature of the QD sample.
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