We show that two major carrier excitation mechanisms are present in II-VI self-assembled quantum dots. The first one is related to direct excited state–ground state transition. It manifests itself by the presence of sharp and intense lines in the excitation spectrum measured from single quantum dots. Apart from these lines, we also observe up to four much broader excitation lines. The energy spacing between these lines indicates that they are associated with absorption related to longitudinal optical phonons. By analyzing resonantly excited photoluminescence spectra, we are able to separate the contributions from these two mechanisms. In the case of CdTe dots, the excited state–ground state relaxation is important for all dots in ensemble, while phonon-assisted processes are dominant for the dots with smaller lateral size.
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We gratefully acknowledge the financial support of the National Science Foundation through grants NSF DMR 0071797, 9975655 and 0072897 and the DARPA-SPINS Program. Work in Poland supported by PBZ-KBN-044/P03/2001.
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Nguyen, T.A., Mackowski, S., Rho, H. et al. Resonant photoluminescence and excitation spectroscopy of CdSe/ZnSe and CdTe/ZnTe self-assembled quantum dots. MRS Online Proceedings Library 737, 92 (2002). https://doi.org/10.1557/PROC-737-E9.2