Photon correlation studies of charge variation in a single GaAlAs quantum dot

B. Piętka, J. Suffczyński, M. Goryca, T. Kazimierczuk, A. Golnik, P. Kossacki, A. Wysmolek, J. A. Gaj, R. Stępniewski, and M. Potemski

Phys. Rev. B 87, 035310 – Published 22 January 2013

Abstract

Complex charge variation processes in low-density, direct-type GaAlAs quantum dots embedded in a type-II GaAs/AlAs bilayer are studied by single-photon correlation measurements. Two groups of excitonic transitions are distinguished in the single quantum dot (QD) photoluminescence spectra, namely due to recombination of neutral and charged multiexcitonic complexes. The radiative cascades are found within each group. Three characteristic time scales are identified in the QD emission dynamics. The fastest one (of the order of 1 ns) is related to excitonic radiative recombination. The two remaining ones are related to the QD charge state variation. The one of 100-ns range (typical blinking time scale) corresponds to random capture of single carriers under a quasiresonant excitation. The slowest processes, in the range of seconds, are related to charge fluctuations in the surrounding of the dot.

Received 18 October 2012

DOI:https://doi.org/10.1103/PhysRevB.87.035310

Authors & Affiliations

B. Piętka^1,2,*, J. Suffczyński¹, M. Goryca¹, T. Kazimierczuk¹, A. Golnik¹, P. Kossacki¹, A. Wysmolek¹, J. A. Gaj^1,†, R. Stępniewski¹, and M. Potemski²

¹Faculty of Physics, University of Warsaw, Warsaw, Poland
²Grenoble High Magnetic Field Laboratory, CNRS, Grenoble, France

^*barbara.pietka@fuw.edu.pl
^†Deceased.

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 87, Iss. 3 — 15 January 2013

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
Representative micro-PL spectra of our single QD at different intensities of quasiresonant excitation. The emission lines indicated as $X$ , $X X$ , and $X^{-}$ are, respectively, due to exciton, biexciton, and negatively charged exciton recombination. The spectrum measured at the highest excitation power illustrates the recombination processes associated with $s$ , $p$ , and $d$ confined shells of the dot. Inset: Scheme of the potential profile along the growth direction of the active part of the GaAs/AlAs type-II bilayer (right panel) and of the corresponding gallium-rich inclusions (left panel). Solid and dotted lines illustrate the states with $Γ$ and $X$ symmetry, respectively. Single excitons confined in our dots provide emission lines in the 1.56–1.72 eV energy range.Reuse & Permissions
Figure 2
(a), (b) $X - X^{-}$ cross-correlation histograms under nonresonant (above 1.75 eV, that is, above the QD barriers) and quasiresonant (below 1.75 eV, that is, below the QD barriers) excitation. (c) $X - X$ photon correlation histogram for the same excitation power and excitation energy as (b). The same long-time-scale correlation evidenced in (b) and (c) histograms indicates that the QD state switches only between neutral and one type of charged configuration of carriers (corresponding to a majority carrier in $X^{-}$ ).Reuse & Permissions
Figure 3
$X - X$ autocorrelation histograms for different excitation powers taken at quasiresonant excitation. The dashed lines represent the fit with the exponential curve (Ref. 1): coincidence counts $(τ) \sim g^{(2)} (τ) \sim 1 - exp (- τ / τ_{d})$ . The parameter $1 / τ_{d}$ represents the charge variation time in the investigated system.Reuse & Permissions
Figure 4
Typical emission spectra of a single GaAlAs quantum dot at moderate excitation power at quasiresonant excitation (a QD different than the one presented in Fig. 1). The emission of the QD switches between two sets of transitions, due to recombination of neutral (solid black line) and charged (dotted green line) QD states.Reuse & Permissions
Figure 5
The set of autohistograms and cross histograms of correlated counts as a function of time interval $τ = τ_{START} - τ_{STOP}$ between photon registration events in start and stop detectors, tuned to indicated excitonic transitions as indicated in each panel (start-stop order). The corresponding emission lines are shown in Fig. 4. The unnormalized intensity scale is different for each histogram. Quasiresonant excitation was used.Reuse & Permissions
Figure 6
Map of the $Γ$ correlation coefficient matrix for a number of consecutively measured micro-PL spectra. The color scale illustrates positive $Γ = + 1$ (white) and negative $Γ = - 1$ (black) correlations, respectively. The average of all the recorded spectra is shown at the top and on the right-hand side of the map.Reuse & Permissions

Physical Review B

covering condensed matter and materials physics