Time-resolved Raman measurements of intersubband relaxation in GaAs quantum wells

Tatham, M.C.; Ryan, John F.; Foxon, C.T.

doi:10.1103/physrevlett.63.1637

Cited by 282 publications

(60 citation statements)

References 12 publications

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“…36 The red-shifted peak position for pulsed excitation indicates not only the existence of localized states in these strained samples 19 but also band-gap renormalization. 40,41 We also note that the effect of band-gap renormalization was stronger at 150 fs pulse but the difference between 150 fs and 30 ps was almost suppressed above 25 T. The 150 fs pulse creates carriers more abruptly than 30 ps pulse and the following carrier-carrier interactions will be enhanced to screen the excitonic Coulomb interactions more effectively. The disappearance of the peak energy separation between 150 fs and 30 ps above 25 T, therefore, could be possibly associated with combined effects of increased carrier density and reduced screening effects because of more strongly confined wave functions via B increment.…”

Section: Pump Pulse-width Dependencementioning

confidence: 78%

“…As discussed earlier, 30 ps is much longer than the estimated delay time t d to build coherence within L c in our system and the intrarelaxation time on the order of 500 fs. 40 Since the increment of linewidth with B was a signature of SF, the observed plateau in the linewidth trace for 30 ps pumping in Fig. 8͑c͒ implies saturated amplified spontaneous emission, not reaching the SF regime yet.…”

Section: Pump Pulse-width Dependencementioning

confidence: 99%

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Cooperative recombination of electron-hole pairs in semiconductor quantum wells under quantizing magnetic fields

et al. 2010

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We present results of detailed investigations of light emission from semiconductor multiple quantum wells at low temperatures and high magnetic fields excited by intense femtosecond laser pulses. The intensity and linewidth as well as the directional and statistical properties of photoemission strongly depended on the magnetic field strength and pump laser fluence. We also investigated the effects of spot size, temperature, excitation geometry, and excitation pulse width on the emission properties. The results suggest that the initially incoherent photoexcited electron-hole pairs spontaneously form a macroscopic coherent state upon relaxation into the low-lying magnetoexcitonic states, followed by the emission of a superfluorescent burst of radiation. We have developed a theoretical model for superfluorescent emission from semiconductor quantum wells, which successfully explained the observed characteristics.

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Section: Pump Pulse-width Dependencementioning

confidence: 78%

Section: Pump Pulse-width Dependencementioning

confidence: 99%

Cooperative recombination of electron-hole pairs in semiconductor quantum wells under quantizing magnetic fields

et al. 2010

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“…4 (b) displays the clear trend of increasing linewidths for 130 fs in contrast to those for 30 ps. 30 ps is much longer than the estimated coherence buildup time for SF in our system ( 10 ps) ～ [3,8] and the intra-relaxation time on the order of 500 fs [16]. Since the increment of linewidth with B was a signature of SF [8], plateau in the linewidth trace for 30 ps implies the saturated amplified spontaneous emission, not reaching SF regime.…”

Section: Resultsmentioning

confidence: 91%

Superfluorescence from Magnetically Formed Quantum Dots: the Excitation Pulse-Width Dependence

Jho¹,

Lee²,

Sanders³

et al. 2008

Journal of the Optical Society of Korea

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We investigated the laser pulse-width dependence of dense plasmas confined within the magnetic length of In0.2Ga0.8As/GaAs multiple quantum wells under high magnetic fields up to 31 T. To fully fill the Landau levels of effectively zero-dimensional system, we used intense femtosecond (fs) laser pulses to create carrier densities near 10 13 /cm 2 . The observed photoluminescence showed a characteristic of superfluorescence, above critical magnetic field when being excited by pulses shorter than coherence buildup time.

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“…This finding is agreement with experimental and theoretical studies of the intersubband relaxation in GaAs/AlGaAs quantum wells, which revealed relaxation times as short as 160 fs to 2 ps when the subband splitting became larger than the threshold energy for LO phonon emission. 29,30 In our case, the fast relaxation via GaAs phonons rather than InAs phonons is explained by the fact that the GaAs phonon modes are only weakly perturbated by the thin InAs layer and that the wave functions of the confined hh and lh states extend entirely into the GaAs matrix. This has previously been demonstrated in resonant luminescence experiments 34,35 on a sample similar to that used in this study.…”

Section: Results and Discussion Of The Carrier Capturementioning

confidence: 98%

“…As the wave functions of the confined InAs layer states extend entirely into the GaAs matrix, the capture process and the intersubband relaxation are well described by assuming GaAs bulk phonons. Both properties should give rise to a fast relaxation of carriers from a lh level to a hh level by LO phonon emission 29,30 within less than 1-2 ps. In contrast, when the hh-lh level separation becomes smaller than the LO phonon energy, relax lhϪhh should increase to several tens of picoseconds.…”

Section: Results and Discussion Of The Carrier Capturementioning

confidence: 99%

Carrier capture in ultrathin InAs/GaAs quantum wells

et al. 2000

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The carrier capture into ultrathin InAs layers embedded in a GaAs matrix has been investigated by timeresolved two-wavelength pump-probe phototransmission at 4.2 K. Using an InAs thickness of 1.2 monolayers, we observe switching of the carrier relaxation from optical to acoustic phonon emission. At the light-hole ͑lh͒ exciton transition we find a constant capture time of 20 ps. In contrast, the capture time decreases abruptly from 50 ps to 22 ps within the heavy-hole ͑hh͒ exciton transition as the energy separation between lh and hh states exceeds the threshold for GaAs LO phonon emission. The combination of both characteristics provides strong evidence for a two-step capture process of the holes. First the holes are captured by the weakly confined lh state and then they cool down to the hh state. We calculated the transient bleaching of the excitonic absorption considering both phase-space filling and exciton screening. The calculations show in agreement with the measurements that the phototransmission transients directly reflect the population of the confined InAs states only at excitation densities below 3ϫ10 8 cm Ϫ2 . At larger excitation densities, the phototransmission rise time becomes significantly smaller than the capture times whereas its decay time appears longer than the carrier lifetime.

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Time-resolved Raman measurements of intersubband relaxation in GaAs quantum wells

Cited by 282 publications

References 12 publications

Cooperative recombination of electron-hole pairs in semiconductor quantum wells under quantizing magnetic fields

Cooperative recombination of electron-hole pairs in semiconductor quantum wells under quantizing magnetic fields

Superfluorescence from Magnetically Formed Quantum Dots: the Excitation Pulse-Width Dependence

Carrier capture in ultrathin InAs/GaAs quantum wells

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