Carrier-transfer dynamics between neutral and charged excitonic states in a single quantum dot probed with second-order photon correlation measurements

H. Nakajima, H. Kumano, H. Iijima, S. Odashima, and I. Suemune

Phys. Rev. B 88, 045324 – Published 31 July 2013

Abstract

We report a comprehensive investigation of carrier-transfer dynamics in a single InAs quantum dot (QD) based on second-order photon correlation measurements. The experimentally obtained auto and crosscorrelation functions as well as photoluminescence intensities are successfully explained on the basis of a series of rate equations with common excitation and also single-carrier-capture/escape rates to/from a QD. This approach enables us to understand the carrier-transfer dynamics responsible for the stability of a quantum two-level system formed in a single QD under various excitation conditions. We clarify that the transition between neutral and charged excitonic states is suppressed by one order of magnitude under quasiresonant excitation.

Received 2 May 2013

DOI:https://doi.org/10.1103/PhysRevB.88.045324

Authors & Affiliations

H. Nakajima^1,2,*, H. Kumano¹, H. Iijima¹, S. Odashima¹, and I. Suemune¹

¹Research Institute for Electronic Science, Hokkaido University, N21W10, Kita-ku, Sapporo 001-0021, Japan
²Research Fellow of the Japan Society for the Promotion of Science, 1-8, Chiyoda-ku, Tokyo 102-8472, Japan

^*nakajima@es.hokudai.ac.jp

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Issue

Vol. 88, Iss. 4 — 15 July 2013

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Images

Figure 1
(a) $μ$ -PL spectrum from a InAs QD at 20 K with an excitation power of 65 $μ$ W. $X^{0}$ , $X X^{0}$ , and $X^{-}$ emissions were observed. (b) $μ$ -PL spectrum with $H$ (V) polarization detection denoted by red circles (blue triangles). Origins of the horizontal axes are set at the mean energies for each emission line. (c) Temporal profiles for the three emission lines. Dotted lines indicates the response function of our measurement system. In the present QD, single exponential population decay is observed. Thus the bright to dark state transitions (Refs. 35 and 36) are discarded in this study.Reuse & Permissions
Figure 2
Second-order photon correlation functions $g^{(2)} (τ)$ measured with five [start, stop] configurations. Red lines are simulation results based on a rate-equation analysis formulated from the five-level model illustrated in Fig. 3.Reuse & Permissions
Figure 3
Five-level scheme used for the rate-equation analysis of charge-transfer dynamics. $G$ , $γ_{L}$ , $γ_{in(out)}$ , and $γ_{in(out)}^{'}$ are exciton photogeneration rate, radiative recombination rate of the line $L$ ( $L = X^{0}, X X^{0}, X^{-}$ ), single-electron capture (escape) rate, and single-hole capture (escape) rate, respectively. For the excitation quasiresonantly to $X^{0}$ , $G$ 's in $| e^{-}$ $〉 \to | X^{-}$ $〉$ and $| X^{0}$ $〉 \to | X X^{0}$ $〉$ processes are set to zero. Population in each state is denoted by $n_{i}$ ( $i = 1 - 5$ ).Reuse & Permissions
Figure 4
(a) Autocorrelation functions for the $X^{0}$ at three excitation powers. Decay of the bunching peak at $τ \sim 0$ becomes slower as the excitation power decreases. (b) Steady-state solutions of the rate equations (triangles) compared with measured PL intensities for $X^{0}$ and $X^{-}$ emissions (circles). Circles (triangles) indicate the integrated PL intensities (calculation). Right axis is obtained after appropriate scaling to the PL intensity.Reuse & Permissions
Figure 5
(a) $μ$ -PL spectrum under quasiresonant excitation with the same QD at 20 $μ$ W excitation. $X^{0}$ is exclusively populated. $μ$ -PLE spectrum with $X^{0}$ emission is shown in the inset. (b) Autocorrelation functions for $X^{0}$ under quasiresonant excitation. Slower decay of the bunching peaks is distinct in comparison to nonresonant excitation. (c) Steady-state solutions (triangles) compared with measured PL intensities for $X^{0}$ and $X^{-}$ emissions (circles). In contrast to Fig. 4b, the $| X^{0}$ $〉$ state is predominantly populated.Reuse & Permissions
Figure 6
Summary of single-electron capture rates ( $γ_{in}$ ) evaluated under various excitation conditions. Transverse axis indicates an effective exciton population. Under quasiresonant excitation, $γ_{in}$ is suppressed by one order of magnitude. Dashed lines are guides to the eye.Reuse & Permissions

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