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Blom, Paul W. M.; Hall, P. J. van; Smit, C.; Cuypers, J. P.; Wolter, J.H.

doi:10.1103/physrevlett.71.3878

Cited by 60 publications

(32 citation statements)

References 25 publications

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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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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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“…Monitoring the time-dependent photoluminescence (PL) collected at the 1s-exciton resonance therefore yields information about the dynamics of these exciton populations. The build-up of the PL after nonresonant excitation has been interpreted as build-up of an incoherent exciton population 5,6,7,8,9,10 , and the subsequent fall off was taken as evidence for this population decay 2,11 . However, a recently developed microscopic luminescence theory for a Coulomb correlated plasma of electron-hole pairs predicts that luminescence peaks at the 1s-exciton resonance even without the presence of incoherent exciton populations 12 .…”

Section: Introductionmentioning

confidence: 99%

Many-body dynamics and exciton formation studied by time-resolved photoluminescence

et al. 2005

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The dynamics of exciton and electron-hole plasma populations is studied via time-resolved photoluminescence after nonresonant excitation. By comparing the peak emission at the exciton resonance with the emission of the continuum, it is possible to experimentally identify regimes where the emission originates predominantly from exciton and/or plasma populations. The results are supported by a microscopic theory which allows one to extract the fraction of bright excitons as a function of time.

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“…1 For a long time, photoluminescence (PL) at the spectral position of the 1s exciton resonance has been considered as evidence for the existence of excitons. The rise of the 1s PL after nonresonant excitation of a semiconductor was interpreted as buildup of an excitonic population [1,2,3,4,5,6], and the PL decay was used to describe exciton recombination [7,8]. However, recently a microscopic theory predicted that PL at the 1s resonance can also originate from correlated plasma emission [9].…”

Section: Introductionmentioning

confidence: 99%

Excitonic Photoluminescence in Semiconductor Quantum Wells: Plasma versus Excitons

et al. 2004

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Time-resolved photoluminescence spectra after nonresonant excitation show a distinct 1s resonance, independent of the existence of bound excitons. A microscopic analysis identifies excitonic and electron-hole plasma contributions. For low temperatures and low densities the excitonic emission is extremely sensitive to even minute optically active exciton populations making it possible to extract a phase diagram for incoherent excitonic populations. 1 For a long time, photoluminescence (PL) at the spectral position of the 1s exciton resonance has been considered as evidence for the existence of excitons. The rise of the 1s PL after nonresonant excitation of a semiconductor was interpreted as buildup of an excitonic population [1,2,3,4,5,6], and the PL decay was used to describe exciton recombination [7,8]. However, recently a microscopic theory predicted that PL at the 1s resonance can also originate from correlated plasma emission [9]. Accordingly, PL at the spectral position of the 1s resonance would not prove the existence of excitons, and previous interpretations may be in question. Indeed, in nonresonantly excited time resolved PL measurements the 1s resonance is developed on a sub-ps timescale at 100 K [10], much faster than any expected exciton formation time.Information about exciton formation can be gained by performing THz experiments [11].However, currently the THz results are inconclusive: Kaindl et al. [12] observed the buildup of the induced absorption corresponding to the excitonic 1s to 2p transition showing excitonic populations with formation times on a rather slow timescale of 100's of ps to ns. They claim to observe a nearly completely excitonic system 1 ns after excitation, while Chari et al. [13] only plasma contributions. Also, THz absorption is sensitive to both dark and bright excitons, and cannot answer if and how excitonic populations influence the PL.Here we address the following questions. Is the 1s PL ever dominated by plasma emission?If so, is it always dominated by plasma emission, i.e. what can we learn about excitonic populations from the 1s PL and nonlinear absorption?After ps continuum excitation, time resolved PL and corresponding probe absorption measurements are performed under identical conditions on a ns timescale. The sample (DBR42) consists of 20 MBE-grown 8 nm In 0.06 Ga 0.94 As quantum wells with 130 nm GaAs barriers; both sides are anti-reflection coated. This indium concentration places the 1s exciton resonance at 1.471 eV at 4 K, avoiding absorption in the bulk GaAs substrate that leads to impurity emission at 1.492 eV from unintentional carbon in the substrate. The results, checked on several other samples including a sample grown in a different MBE system, are insensitive to exciton linewidths or to interfacial or alloy disorder. Single-quantum-well data were noisier but exhibited a similar behavior, excluding significant radiative coupling effects.We excite nonresonantly 13.2 meV above the 1s resonance, into the heavy-hole continuum but below the light-h...

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Selective exciton formation in thin GaAs/AlxGa1−

Cited by 60 publications

References 25 publications

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

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

Many-body dynamics and exciton formation studied by time-resolved photoluminescence

Excitonic Photoluminescence in Semiconductor Quantum Wells: Plasma versus Excitons

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