Intra-dot relaxation and dephasing rates from time-resolved photoluminescence from InAs quantum dot ensembles

An ensemble of InAs quantum dots with ground state transition energies centered at 1.216 eV and density 10 11dots/cm 2 has been studied by time-resolved photoluminescence (PL). The wavelength of the 100-fs excitation pulse was tuned through the ground (excited) state transitions, resulting in resona...

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Bibliographic Details
Published in:Solid state communications 2009-09, Vol.149 (35), p.1485-1492
Main Authors: Chernikov, Alexej, Horst, Swantje, Koch, Stephan W., Chatterjee, Sangam, Rühle, Wolfgang W., Sweet, Julian, Richards, Benjamin, Hendrickson, Josh, Khitrova, Galina, Gibbs, Hyatt M., Litvinov, Dimitri, Gerthsen, Dagmar, Wegener, Martin
Format: Article
Language:English
Subjects:
B. III–V semiconductors
C. Quantum dots (optical properties)
D. Time resolved luminescence
E. High-resolution transmission electron microscopy (HRTEM)
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Summary:An ensemble of InAs quantum dots with ground state transition energies centered at 1.216 eV and density 10 11dots/cm 2 has been studied by time-resolved photoluminescence (PL). The wavelength of the 100-fs excitation pulse was tuned through the ground (excited) state transitions, resulting in resonant (optical phonon sideband) PL. The decay of the PL was time resolved with a streak camera in the interval 1.5–3 ns to avoid scattered laser light. The intensity of the PL was recorded with its polarization both parallel with and perpendicular to the excitation polarization (along one of the crystal’s cleave axes); the ratio is 2.22 at low temperatures and low excitation. A phenomenological rate equation analysis is made, separating the excitations into two classes, one polarized along the excitation polarization and the other unpolarized (either that way immediately after the excitation pulse or scattered from the first class). Excellent fits to the data lead to the conclusion that both classes decay radiatively with a lifetime of 1 ns, and a transfer from the polarized to the unpolarized species takes place with a distribution time of 12 ns at low temperatures and low excitation, dropping rapidly toward zero for temperatures above 30 K and for intense excitation levels. The polarization of a coherently excited ground state exciton should dephase with a rate equal to the sum of the radiative rate plus the inverse of this distribution time.
ISSN:0038-1098
1879-2766
DOI:10.1016/j.ssc.2009.04.041