Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical review. B, Condensed matter

Density-dependent exciton radiative lifetimes in GaAs quantum wells

R. Eccleston, B. F. Feuerbacher, J. Kühl, Wolfgang W. Rühle, Klaus Ploog

Published May 15, 1992• 84 citations
Publisher

Abstract

Resonant photoexcitation of a predominantly homogeneously broadened exciton line in a GaAs quantum well results in a nonexponential time-resolved photoluminescence decay transient due to the decrease in the exciton-exciton scattering contribution to the homogeneous linewidth, ${\mathrm{\ensuremath{\Gamma}}}_{\mathit{h}}$, as the exciton population decays. This result confirms the theoretically predicted relationship between the exciton radiative recombination lifetime and the homogenous linewidth (and coherence area) of the exciton state.

DOI
10.1103/physrevb.45.11403

Related papers

Increase in Exciton Radiative Lifetime in GaAs Quantum Wells at High Exciton Density due to Exciton-Exciton Scattering

R. Eccleston, B. F. Feuerbacher, J. Kühl +2 more

We report time-resolved photoluminescence (TRPL) measurements of the radiative lifetime (τr) at 1.8K of resonantly excited heavy-hole excitons in a 27nm GaAs single quantum well as a function of exciton density. By the use of AlAs interface smoothing layers [1], the sample exhibits very little inhomogeneous broadening (≈0.15meV). The exciton centre of mass motion is therefore not significantly restricted by localisation in well width fluctuation islands. However, measurements of the exciton homogeneous linewidth (Γ h ) using time-resolved degenerate four wave mixing in the self-diffraction configuration (Fig.1) [2], additionally show that the sample imperfection scattering contribution to the Γ h of these delocalised excitons is also small (0.2meV). Thus, as indicated by the dependence of Γ h on exciton density (N x ), even at moderate exciton densities, exciton-exciton scattering is the dominant dephasing interaction within the photocreated exciton ensemble.

International Conference on Ultrafast Phenomena•Jan 1, 1992•0 citations

Excitation- and Disorder-induced Reduction of the Superradiant Excitonic Decay in GaAs Quantum Well Bragg Structures

J. Kühl, Matthias Hübner, T. Stroucken +5 more

The theoretically predicted rapid superradiant decay of coherent 2D excitons on a time scale of approximately 10 ps [1] is expected to be strongly enhanced in multiple QW (MQW) Bragg structures consisting of N identical QWs separated by (Ga,Al)As barriers the thickness of which was adjusted so that the QWs had a distance d equal to one half of the heavy-hole exciton resonance wavelength λ in the medium [2]. This enhancement originates from efficient radiative coupling of excitons excited in different wells via the exchange of transverse photons. Recently we have published [3] degenerate-four-wave-mixing experiments with fs optical pulses on GaAs QW Bragg structures which demonstrate that the radiative lifetime in high-quality GaAs single QWs (SQW) is approximately 5 ps and decreases to less than 2 ps in Bragg samples with N=10. These studies revealed that radiative recombination provides the dominant contribution to the homogenous linewidth of the 2D exciton in high-quality samples and exceeds nonradiative contributions caused by scattering with sample imperfections in contrast to previous assumptions.

Quantum Optoelectronics•Jan 1, 1997•0 citations

Coherent transient in photoluminescence of excitonic molecules in GaAs quantum wells

A. L. Ivanov, Hailin Wang, Jagdeep Shah +4 more

Time-resolved photoluminescence (PL) of excitonic molecules in GaAs quantum wells (QW's) reveals an initial transient characterized by a finite rise and an extremely fast nonexponential decay [H. Wang, J. Shah, and T. C. Damen et al., Solid State Commun. 98, 807 (1996)]. The transient is attributed to coherent quantum evolution towards the molecule ground state of two optically correlated excitons, ${\ensuremath{\sigma}}^{+}$ and ${\ensuremath{\sigma}}^{\ensuremath{-}},$ which undergo the Coulombic attraction. In the present paper, we develop a theory of the transient PL and fit the experimental data. The radiative decay of a quasi-two-dimensional (2D) excitonic molecule is analyzed with the giant oscillator strength model adapted to QW's and with the bipolariton model. Within the 2D bipolariton model, the main ``hidden'' channel of the radiative decay of an excitonic molecule is the resonant dissociation into two outgoing interface (surface) polaritons rather than the observable decay into the bulk radiative modes. We conclude that quasi-2D molecules dissociate already within the initial transient of PL, while the following exponential decay of the molecule-mediated PL is due to the escape of secondary interface polaritons into the bulk modes. According to the 2D bipolariton model, the sequence ``two incoming $\mathrm{photons}\ensuremath{\rightarrow}\mathrm{two}$ virtual $\mathrm{excitons}\ensuremath{\rightarrow}2\mathrm{D}$ $\mathrm{molecule}\ensuremath{\rightarrow}\mathrm{two}$ outgoing interface polaritons'' is a completely coherent process. The fit of the time-resolved molecule-mediated PL provides us with numerical estimates of the exciton-photon coupling in GaAs QW's.

Physical review. B, Condensed matter•Aug 15, 1997•23 citations

Ultrafast secondary radiation of excitons in quantum wells: The transition from the coherent to the incoherent regime

Stefan Haacke, Gary R. Hayes, Robert Anthony Taylor +2 more

Coherent Rayleigh scattering and incoherent luminescence are studied by femtosecond upconversion under resonant excitation as a function of exciton density in GaAs quantum wells. Comparing samples with different well widths allows to establish the relation between inhomogeneous broadening and the shape of resonant Rayleigh scattering. We find an excellent agreement between experiment and a classical model. In samples with moderate inhomogeneous broadening we provide evidence for the transition from coherent to incoherent emission. The comparison with excitonic dephasing times T2 obtained from four-wave-mixing experiments demonstrates that the incoherent exciton population rises within T2/2, at any exciton density when changed by more than an orders of magnitude. The experimental results confirm very clearly the concept predicting that the coherent polarization made up by localized excitons decays into an incoherent exciton population under conservation of the number of excited quanta.

Radiative Processes and Dephasing in Semiconductors•Jan 1, 1998•0 citations

Enhanced radiative recombination of free excitons in GaAs quantum wells

B. Deveaud, Fabrice Clérot, N. Roy +3 more

Radiative properties of free excitons in a single GaAs quantum well are studied under resonant excitation. Enhanced radiative recombination of the excitons, caused by the breakdown of the translational symmetry of the system, is evidenced by the very short lifetime as well as by the strong intensity of the signal. Dephasing mechanisms, by transferring the excitons to nonradiative states, increase the observed lifetime. We deduce a radiative lifetime of 10\ifmmode\pm\else\textpm\fi{}4 ps in the absence of dephasing mechanisms.

Physical Review Letters•Oct 1, 1991•372 citations

RELATION BETWEEN HOMOGENEOUS LINEWIDTH AND RADIATIVE LIFETIME OF EXCITONS IN QUANTUM WELLS

A. Honold, Lothar Schultheis, J. Kühl +1 more

At low excitation intensities the transmission and luminescence spectra of high quality direct gap semiconductor quantum wells are dominated by exciton transitions. The dynamics of these excitons is characterized by different relaxation times like the phase coherence time T2 and the recombination lifetime τ. The recombination lifetime of such two-dimensional (2D) excitons as well as its variation with the quantum well thickness L2 and the temperature T has been studied extensively by means of time-resolved photolumiaescence.1 On the other hand much less information is available for the phase coherence time T2 and the corresponding homogeneous linewidth Γh of these excitons because of the more complicated methods needed to measure it.2 The phase coherence time T2 is sensitive to all interactions of the excitons and, therefore, phase relaxation normally appears on a much shorter time scale than recombination.

•Jul 18, 1988•1 citation
Resonant photoexcitation of a predominantly homogeneously broadened exciton line in a GaAs quantum well results in a nonexponential time-resolved photoluminescence decay transient due to the decrease in the exciton-exciton scattering contribution to the homogeneous linewidth, \ensuremathΓh{\mathrm{\ensuremath{\Gamma}}}_{\mathit{h}}\ensuremathΓh​, as the exciton population decays. This result confirms the theoretically predicted relationship between the exciton radiative recombination lifetime and the homogenous linewidth (and coherence area) of the exciton state.
We report time-resolved photoluminescence (TRPL) measurements of the radiative lifetime (τr) at 1.8K of resonantly excited heavy-hole excitons in a 27nm GaAs single quantum well as a function of exciton density. By the use of AlAs interface smoothing layers [1], the sample exhibits very little inhomogeneous broadening (≈0.15meV). The exciton centre of mass motion is therefore not significantly restricted by localisation in well width fluctuation islands. However, measurements of the exciton homogeneous linewidth (Γ h ) using time-resolved degenerate four wave mixing in the self-diffraction configuration (Fig.1) [2], additionally show that the sample imperfection scattering contribution to the Γ h of these delocalised excitons is also small (0.2meV). Thus, as indicated by the dependence of Γ h on exciton density (N x ), even at moderate exciton densities, exciton-exciton scattering is the dominant dephasing interaction within the photocreated exciton ensemble.
The theoretically predicted rapid superradiant decay of coherent 2D excitons on a time scale of approximately 10 ps [1] is expected to be strongly enhanced in multiple QW (MQW) Bragg structures consisting of N identical QWs separated by (Ga,Al)As barriers the thickness of which was adjusted so that the QWs had a distance d equal to one half of the heavy-hole exciton resonance wavelength λ in the medium [2]. This enhancement originates from efficient radiative coupling of excitons excited in different wells via the exchange of transverse photons. Recently we have published [3] degenerate-four-wave-mixing experiments with fs optical pulses on GaAs QW Bragg structures which demonstrate that the radiative lifetime in high-quality GaAs single QWs (SQW) is approximately 5 ps and decreases to less than 2 ps in Bragg samples with N=10. These studies revealed that radiative recombination provides the dominant contribution to the homogenous linewidth of the 2D exciton in high-quality samples and exceeds nonradiative contributions caused by scattering with sample imperfections in contrast to previous assumptions.
Time-resolved photoluminescence (PL) of excitonic molecules in GaAs quantum wells (QW's) reveals an initial transient characterized by a finite rise and an extremely fast nonexponential decay [H. Wang, J. Shah, and T. C. Damen et al., Solid State Commun. 98, 807 (1996)]. The transient is attributed to coherent quantum evolution towards the molecule ground state of two optically correlated excitons, ${\ensuremath{\sigma}}^{+}$ and ${\ensuremath{\sigma}}^{\ensuremath{-}},$ which undergo the Coulombic attraction. In the present paper, we develop a theory of the transient PL and fit the experimental data. The radiative decay of a quasi-two-dimensional (2D) excitonic molecule is analyzed with the giant oscillator strength model adapted to QW's and with the bipolariton model. Within the 2D bipolariton model, the main ``hidden'' channel of the radiative decay of an excitonic molecule is the resonant dissociation into two outgoing interface (surface) polaritons rather than the observable decay into the bulk radiative modes. We conclude that quasi-2D molecules dissociate already within the initial transient of PL, while the following exponential decay of the molecule-mediated PL is due to the escape of secondary interface polaritons into the bulk modes. According to the 2D bipolariton model, the sequence ``two incoming $\mathrm{photons}\ensuremath{\rightarrow}\mathrm{two}$ virtual $\mathrm{excitons}\ensuremath{\rightarrow}2\mathrm{D}$ $\mathrm{molecule}\ensuremath{\rightarrow}\mathrm{two}$ outgoing interface polaritons'' is a completely coherent process. The fit of the time-resolved molecule-mediated PL provides us with numerical estimates of the exciton-photon coupling in GaAs QW's.
Coherent Rayleigh scattering and incoherent luminescence are studied by femtosecond upconversion under resonant excitation as a function of exciton density in GaAs quantum wells. Comparing samples with different well widths allows to establish the relation between inhomogeneous broadening and the shape of resonant Rayleigh scattering. We find an excellent agreement between experiment and a classical model. In samples with moderate inhomogeneous broadening we provide evidence for the transition from coherent to incoherent emission. The comparison with excitonic dephasing times T2 obtained from four-wave-mixing experiments demonstrates that the incoherent exciton population rises within T2/2, at any exciton density when changed by more than an orders of magnitude. The experimental results confirm very clearly the concept predicting that the coherent polarization made up by localized excitons decays into an incoherent exciton population under conservation of the number of excited quanta.
Radiative properties of free excitons in a single GaAs quantum well are studied under resonant excitation. Enhanced radiative recombination of the excitons, caused by the breakdown of the translational symmetry of the system, is evidenced by the very short lifetime as well as by the strong intensity of the signal. Dephasing mechanisms, by transferring the excitons to nonradiative states, increase the observed lifetime. We deduce a radiative lifetime of 10\ifmmode\pm\else\textpm\fi{}4 ps in the absence of dephasing mechanisms.
At low excitation intensities the transmission and luminescence spectra of high quality direct gap semiconductor quantum wells are dominated by exciton transitions. The dynamics of these excitons is characterized by different relaxation times like the phase coherence time T2 and the recombination lifetime τ. The recombination lifetime of such two-dimensional (2D) excitons as well as its variation with the quantum well thickness L2 and the temperature T has been studied extensively by means of time-resolved photolumiaescence.1 On the other hand much less information is available for the phase coherence time T2 and the corresponding homogeneous linewidth Γh of these excitons because of the more complicated methods needed to measure it.2 The phase coherence time T2 is sensitive to all interactions of the excitons and, therefore, phase relaxation normally appears on a much shorter time scale than recombination.