Reduced dimensionality of hot-carrier relaxation in GaAs quantum wells

Leo, K.; Rühle, W. W.; Hj, Queisser; Ploog, K.

doi:10.1103/physrevb.37.7121

Cited by 55 publications

(37 citation statements)

References 20 publications

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“…We show that from the investigation of the dynamics of the experimental PL spectra alone, one can clearly distinguish two regimes with and without major exciton contributions. This confirms our previous result that above 30 K the emission at the 1s-resonance is dominantly due to unbound pair-state emission, while for temperatures lower than 30 K an increasing optically active exciton population contributes 17 . We support our experimental results by a microscopic theory leading to the luminescence analogue of the famous Elliott formula 19 .…”

Section: Introductionsupporting

confidence: 92%

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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Section: Introductionsupporting

confidence: 92%

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

et al. 2005

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“…1 are density dependent and vary from 13.5 K at the lowest density to 20.7 K at the highest density. Even at later times, they never reach the lattice value of 4 K [15,16,17]; the lowest temperature measured was 10.5±0.5 K (2.8 ns after excitation for an initial carrier density of n eh = 2.9 × 10 8 cm −2 ).For a lattice temperature of 50 K, our measurements show identical lattice and carrier temperatures after 0.1 ns.To compare many spectra as a function of density and temperature, it is convenient to define a single parameter β to characterize each spectrum. In thermodynamic equilibrium, one expects the PL to be proportional to the absorption coefficient α times a Bose distribu-…”

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confidence: 50%

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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“…Switching now to the electron-hole plasma regime, both in bulk and QWs, time-resolved studies have concentrated in the thermalization [18][19][20] and cooling 21,22 mechanisms of the hot photocreated carriers, but little attention has been paid to the processes responsible for the onset of the luminescence, characterized by its rise time.…”

Section: Introductionmentioning

confidence: 99%

Interplay of exciton and electron-hole plasma recombination on the photoluminescence dynamics in bulk GaAs

et al. 2006

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We present a systematic study of the exciton/electron-hole plasma photoluminescence dynamics in bulk GaAs for various lattice temperatures and excitation densities. The competition between the exciton and electron-hole pair recombination dominates the onset of the luminescence. We show that the metal-to-insulator transition, induced by temperature and/or excitation density, can be directly monitored by the carrier dynamics and the time-resolved spectral characteristics of the light emission. The dependence on carrier density of the photoluminescence rise time is strongly modified around a lattice temperature of 49 K, corresponding to the exciton binding energy (4.2 meV). In a similar way, the rise-time dependence on lattice temperature undergoes a relatively abrupt change at an excitation density of 120-180x10 15 cm -3 , which is about five times greater than the calculated Mott density in GaAs taking into account many body corrections.

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Reduced dimensionality of hot-carrier relaxation in GaAs quantum wells

Cited by 55 publications

References 20 publications

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

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

Excitonic Photoluminescence in Semiconductor Quantum Wells: Plasma versus Excitons

Interplay of exciton and electron-hole plasma recombination on the photoluminescence dynamics in bulk GaAs

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