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Radiative recombination dynamics of CdSe/Zn(S,Se)/MgS quantum dots up to room temperature
Author(s) -
Zaitsev S. V.,
Arians R.,
Kümmell T.,
Bacher G.,
Gust A.,
Kruse C.,
Hommel D.
Publication year - 2010
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200983250
Subject(s) - quantum dot , recombination , exciton , exponential decay , quantum yield , atomic physics , population , spontaneous emission , condensed matter physics , physics , materials science , molecular physics , chemistry , optoelectronics , fluorescence , optics , quantum mechanics , laser , biochemistry , demography , sociology , gene
The recombination dynamics and its temperature dependence are studied in detail in epitaxially grown CdSe/Zn(S,Se) quantum dots (QDs) with additional wide‐band MgS barriers. Such design allows to preserve a very high quantum yield and to track the QD recombination dynamics up to room temperature. At low temperatures, a fast initial decay ∼0.6 ns is observed which is followed by a long decay with a time constant ∼25 ns. The fast initial decay disappears with increasing temperature and above 100 K only a single‐exponential decay is observed with a decay time τ of 1.2–1.5 ns, which is weakly dependent on temperature up to 300 K. A two‐level model including bright and dark exciton states and temperature dependent spin‐flip between them describes well the experimental findings. According to the model, the long decay tail results from a thermally activated population of the bright exciton state from the energetically lowest dark state.