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Spectral broadening and population relaxation in a GaAs interfacial quantum dot ensemble and quantum well nanostructure
Author(s) -
Moody G.,
Siemens M. E.,
Bristow A. D.,
Dai X.,
Karaiskaj D.,
Bracker A. S.,
Gammon D.,
Cundiff S. T.
Publication year - 2011
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.201000816
Subject(s) - quantum dot , nanostructure , condensed matter physics , relaxation (psychology) , quantum , population , materials science , physics , quantum mechanics , psychology , medicine , social psychology , environmental health
Optical two‐dimensional Fourier transform spectroscopy (2DFTS) is used to measure thermal broadening of the ground state exciton homogeneous linewidth and energy relaxation in a single layer of interfacial GaAs quantum dots (QDs). We observe a nonlinear increase in the homogeneous linewidth with temperature from 6 to 50 K and find that a phonon activation term + offset fit the data well. The absence of an activation peak in the 2D spectra indicates that elastic exciton–phonon scattering via virtual transitions between the ground and excited states significantly contributes to the thermal broadening. Measurements of the linewidth across the inhomogeneous distribution show that excitons localized in smaller QDs experience stronger thermal broadening. We record 2D spectra for a population time up to 500 ps and temperature up to 50 K to reveal excitonic relaxation from quantum well to QD states. As the temperature increases from 6 to 50 K, the relaxation time decreases from 180 to 30 ps, respectively. This behavior is consistent with a phonon‐mediated scattering process.