Exciton dynamics in the presence of an electron gas in GaAs quantum wells

Bajoni, Daniele; Senellart, P.; Perrin, Mathieu; Lemaı̂tre, A.; Sermage, B.; Bloch, J.

doi:10.1002/pssb.200668071

Cited by 6 publications

(6 citation statements)

References 12 publications

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“…Our assumption about the photocreation of free carriers is further supported by the observation of a strong broadening of the lowest exciton peak. Indeed, according to Refs., 23,33 the cross-section of exciton-freecarrier scattering is by an order of magnitude larger than that of the exciton-exciton one. So, the exciton relaxation due to exciton-carrier collisions is mainly responsible for the strong broadening of the X1 resonance in the case of excitation above the X lh transition.…”

Section: Discussionmentioning

confidence: 90%

“…Under nonresonant excitation, the PL pulse is characterized by a rise time, τ rise = 10 − 1000 ps, and a decay time, τ decay = 1 − 30 ns, depending on the experimental conditions as well as on the sample design and quality. 3,5,14,[17][18][19][20][21][22][23][24] The theoretical analysis of the data performed in these works and also in Refs. 2,13,15,[25][26][27] al-arXiv:1412.0443v2 [cond-mat.mes-hall] 6 Feb 2015 lowed obtaining characteristic rates of processes occurring mainly in the reservoir of nonradiative excitons.…”

Section: Introductionmentioning

confidence: 99%

“…It was found that, the characteristic time of exciton formation from free carriers lies in the range from several tens to hundreds of picoseconds. 19,23,24,28 The exciton thermalization in the reservoir occurs approximately in the same time range. 13,25,27 These two processes are mainly responsible for the PL rise time in high-quality structures.…”

Section: Introductionmentioning

confidence: 99%

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Nontrivial relaxation dynamics of excitons in high-quality InGaAs/GaAs quantum wells

et al. 2015

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Photoluminescence (PL) and reflectivity spectra of a high-quality InGaAs/GaAs quantum well structure reveal a series of ultra-narrow peaks attributed to the quantum confined exciton states. The intensity of these peaks decreases as a function of temperature, while the linewidths demonstrate a complex and peculiar behavior. At low pumping the widths of all peaks remain quite narrow (< 0.1 meV) in the whole temperature range studied, 4 -30 K. At the stronger pumping, the linewidth first increases and than drops down with the temperature rise. Pump-probe experiments show two characteristic time scales in the exciton decay, < 10 ps and 15 -45 ns, respectively. We interpret all these data by an interplay between the exciton recombination within the light cone, the exciton relaxation from a nonradiative reservoir to the light cone, and the thermal dissociation of the nonradiative excitons. The broadening of the low energy exciton lines is governed by the radiative recombination and scattering with reservoir excitons while for the higher energy states the linewidths are also dependent on the acoustic phonon relaxation processes.

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Section: Discussionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nontrivial relaxation dynamics of excitons in high-quality InGaAs/GaAs quantum wells

et al. 2015

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“…Another approach is the time-resolved spectroscopy using photoluminescence kinetics, pump-probe, or four-wave mixing methods for determination of the radiative decay time, see, e.g., Refs. [12,[16][17][18][19]. Similar problems appear in this approach if the quality of the heterostructure is not high enough.…”

Section: Introductionmentioning

confidence: 90%

Radiative decay rate of excitons in square quantum wells: Microscopic modeling and experiment

Khramtsov

Belov

Grigoryev

et al. 2016

Journal of Applied Physics

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The binding energy and the corresponding wave function of excitons in GaAs-based finite square quantum wells (QWs) are calculated by the direct numerical solution of the three-dimensional Schrödinger equation. The precise results for the lowest exciton state are obtained by the Hamiltonian discretization using the high-order finite-difference scheme. The microscopic calculations are compared with the results obtained by the standard variational approach. The exciton binding energies found by two methods coincide within 0.1 meV for the wide range of QW widths. The radiative decay rate is calculated for QWs of various widths using the exciton wave functions obtained by direct and variational methods. The radiative decay rates are confronted with the experimental data measured for high-quality GaAs/AlGaAs and InGaAs/GaAs QW heterostructures grown by molecular beam epitaxy. The calculated and measured values are in good agreement, though slight differences with earlier calculations of the radiative decay rate are observed.

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“…Such a delayed rise agrees with previous PL studies of exciton formation. 46,50,57,58,59,60,61 The fast initial exciton formation is largely absent in the PL, which indicates that the excitons probed by the THz pulses at early delays primarily populate high energy states with momenta K ≫ 0.…”

Section: B Photoluminescence Dynamicsmentioning

confidence: 99%

Transient terahertz spectroscopy of excitons and unbound carriers in quasi-two-dimensional electron-hole gases

et al. 2009

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We report a comprehensive experimental study and detailed model analysis of the terahertz dielectric response and density kinetics of excitons and unbound electron-hole pairs in GaAs quantum wells. A compact expression is given, in absolute units, for the complex-valued terahertz dielectric function of intra-excitonic transitions between the 1s and higher-energy exciton and continuum levels. It closely describes the terahertz spectra of resonantly generated excitons. Exciton ionization and formation are further explored, where the terahertz response exhibits both intra-excitonic and Drude features. Utilizing a two-component dielectric function, we derive the underlying exciton and unbound pair densities. In the ionized state, excellent agreement is found with the Saha thermodynamic equilibrium, which provides experimental verification of the two-component analysis and density scaling. During exciton formation, in turn, the pair kinetics is quantitatively described by a Saha equilibrium that follows the carrier cooling dynamics. The terahertz-derived kinetics is, moreover, consistent with time-resolved luminescence measured for comparison. Our study establishes a basis for tracking pair densities via transient terahertz spectroscopy of photoexcited quasi-two-dimensional electron-hole gases.

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Exciton dynamics in the presence of an electron gas in GaAs quantum wells

Cited by 6 publications

References 12 publications

Nontrivial relaxation dynamics of excitons in high-quality InGaAs/GaAs quantum wells

Nontrivial relaxation dynamics of excitons in high-quality InGaAs/GaAs quantum wells

Radiative decay rate of excitons in square quantum wells: Microscopic modeling and experiment

Transient terahertz spectroscopy of excitons and unbound carriers in quasi-two-dimensional electron-hole gases

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