Measurement of phonon-assisted migration of localized excitons in GaAs/AlGaAs multiple-quantum-well structures

Wang, H.; Jiang, Min; Steel, Duncan G.

doi:10.1103/physrevlett.65.1255

Cited by 86 publications

(40 citation statements)

References 14 publications

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“…We do not observe contributions from line broadening or frequency shift characteristic of other many-body effects seen in higher dimensional systems [12]. The data, in addition, are profoundly different from studies in wide quantum wells where exciton localization is weak and phonon assisted migration leads to spectral diffusion and excitation of a broad energy distribution of localized excitons at lower energy [13]. We note that measurements with orthogonal polarizations (discussed in detail elsewhere [10]), while leading to complications due to fine structure splitting [3,11], do not show the changes in intensity or dephasing rate seen in quantum wells [14].…”

Section: Form Approved Omb No 0704-0188contrasting

confidence: 88%

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Nonlinear Nano-Optics: Probing One Exciton at a Time

et al. 1998

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Coherent nonlinear optical spectroscopy of individual excitons in GaAs quantum dots is demonstrated and shows strong similarities with atoms in their coherent optical interaction, unlike higher dimensional heterostructures. The nonlinear response is dominated by an incoherent contribution (saturation) and a coherent contribution (population pulsations) of the single dot and compares well with present theory. The data shows that energy relaxation and dephasing rates are comparable, reflecting the absence of significant pure dephasing, and also demonstrate the presence of interdot energy transfer.[S0031-9007(98)07287-1] PACS numbers: 73.20.Fz, 78.47. + p, 78.66.Fd Recent studies of electron-hole excitation in quantum dots (QD) show the consequences of three-dimensional confinement including atomiclike d-function density of states and increased exciton binding energy and oscillator strength. Using photoluminescence (PL) and various microprobing methods to eliminate spectral blurring, numerous groups have now reported sharp line spectra and excited states of individual QD's similar to atoms [1][2][3][4]. In this paper, we combine the breakthrough of single QD probing with the power of nonlinear optical spectroscopy in semiconductors [5] to observe the coherent nonlinear optical response of a single exciton confined in a QD potential. The measurements show the coherent nonlinear interaction with light is atomiclike in nature revealing that the dominant nonlinearity is state filling as predicted in earlier theoretical studies [6]. The work opens up a new direction of research for direct measurements of exciton dynamics in QD's (e.g., dephasing, energy relaxation, interdot coupling, etc.) and optical nonlinearities as well as taking the first step in the direction of demonstrating coherent control and fast switching for novel applications [7]. The data provide a measure of the energy relaxation rates and the dephasing rate and show the absence of significant pure dephasing processes at low temperature. The data also show the contribution to energy relaxation in some dots due to interdot energy transfer. Probing a single exciton demonstrates coherent optical coupling leading to population pulsations of single dots at frequencies above 15 GHz. The measurements show the profound effects of the complete discretization of the energy spectra to the resonant nonlinear response [6] demonstrating the similarity of these dots with atomic systems beyond linear response.Measurements are made at T 6 K on a narrow ͑42 Å͒ single molecular-beam epitaxy (MBE) grown GaAs quantum well with 250 Å Al 0.3 Ga 0.7 As barriers. Growth interrupts at the interfaces lead to the formation of large monolayer-high islands [8] which localize excitons in QD potentials that are 15 monolayers thick with lateral dimensions on the order of 40 nm [3]. Excitons in isolated QD's are probed by exciting through a 0.2-2.5 mm aperture in a 100-nm-thick Al mask deposited directly on the sample surface [3]. The sample is attached to a sapphire disk (c-axis nor...

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Section: Form Approved Omb No 0704-0188contrasting

confidence: 88%

“…Furthermore, the peak of the nearly degenerate response tracks v 1 but occurs between v 0 and v 1 . This is different from the spectral hole burning that is observed in inhomogeneously broadened systems [13]. The behavior in Fig.…”

Section: Form Approved Omb No 0704-0188contrasting

confidence: 62%

Nonlinear Nano-Optics: Probing One Exciton at a Time

et al. 1998

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“…The small positive delay is chosen to minimize the effects of spectral diffusion. 17 The spectrum shows the exciton and biexciton contributions, which have widths of 1.6 and 2.7 meV, respectively. This deconvolves to a biexciton binding energy distribution of 2.2-meV full width at half maximum centered at 8.5 meV.…”

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confidence: 99%

Binding-energy distribution and dephasing of localized biexcitons

1997

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“…From this we conclude that the free-exciton picture fails, and that excitons localize in the low-energy wing, in agreement with earlier findings. 18,26 B. High N ex and T, transport and dephasing By increasing the excitation density N ex and temperature T, we can study the dephasing and transport properties of REE in the presence of interaction.…”

Section: ͑7͒mentioning

confidence: 99%

“…Deveaud et al 17 demonstrated in a time-resolved luminescence experiment that nonresonantly excited excitons move from a region of N monolayers to a region with Nϩ1 monolayers in typically 250 ps. Wang, Jiang, and Steel 18 reported also in GaAs QW's a 100-ps time for the hopping of localized excitons. They employed high-resolution frequency-resolved FWM.…”

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confidence: 99%

Transport of superradiant excitons in GaAs single quantum wells

et al. 1997

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The dynamics of resonantly excited 1s-HH excitons in GaAs single quantum wells is studied by picosecond transient reflection and photon echo. The energy relaxation and transport properties of the excitons are probed, making use of the surface electric field. At low exciton densities and 5 K, transport appears to be absent, and superradiant decay takes the place of free excitons with characteristic times ranging from 5 to 13 ps, depending on the well width. The polarization decay is governed by energy relaxation, and a coherence length is found for these free excitons of ϳ200 nm. Low in the exciton resonance, we measure a much slower radiative decay and smaller coherence lengths, due to localization. Here both radiative decay and pure dephasing contribute to the polarization dephasing rate. At higher exciton densities and temperature, transport is observed, induced by exciton-exciton and exciton-phonon collisions. For free excitons it is demonstrated that the increased polarization dephasing rate is exclusively due to exciton transport, and not to pure dephasing. For localized excitons, pure dephasing processes prevail in T 2 , and thermally activated transport is found. ͓S0163-1829͑97͒05847-5͔

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Measurement of phonon-assisted migration of localized excitons in GaAs/AlGaAs multiple-quantum-well structures

Cited by 86 publications

References 14 publications

Nonlinear Nano-Optics: Probing One Exciton at a Time

Nonlinear Nano-Optics: Probing One Exciton at a Time

Binding-energy distribution and dephasing of localized biexcitons

Transport of superradiant excitons in GaAs single quantum wells

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