Spectroscopy on single buried InAs quantum dots by scattering scanning near-field infrared microscopy


Spectroscopy on single buried InAs quantum dots by scattering scanning near-field infrared microscopy

Fehrenbacher, M.; Jacob, R.; Winnerl, S.; Bhattacharyya, J.; Schneider, H.; Wenzel, M. T.; von Ribbeck, H.-G.; Eng, L. M.; Akinson, P.; Schmidt, O. G.; Helm, M.

Quantum dots are a highly interesting material system for many application purposes such as single photon emitters in the near-infrared, but also for mid- and far-infrared applications. Studying the linewidth of involved optical transitions off ers valuable clues to the dephasing mechanisms of the trapped electrons. However, due to size fluctuations of the quantum dots, inhomogeneous broadening of the signals usually hides this information when investigating ensembles of dots. Therefore, single-dot spectroscopy has to be performed for this purpose. In contrast to studies of interband transitions this is not well established at all for intersublevel transitions. In this work, scattering type scanning near-fi eld optical microscopy (s-SNOM) in combination with a free-electron laser is used to investigate intersublevel transitions in single self-assembled buried InAs quantum dots. Thereby, spectrally resonant optical contrast to the surrounding GaAs substrate is observed at photon energies of 83 meV and 123 meV, which can clearly be assigned to the s-d and p-d transitions of single conduction band electrons.

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Publ.-Id: 19918