Correct determination of low-temperature free-exciton diffusion profiles in GaAs

Bieker, S.; Kießling, T.; Ossau, W.; Molenkamp, L. W.

doi:10.1103/physrevb.92.121201

Cited by 9 publications

(5 citation statements)

References 28 publications

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“…4d , the carrier capture rate from the bulk GaAs decreases rapidly for d < 10 nm because for this thickness, the contribution of carrier diffusion is insignificant. The electron-hole (e-h) capture rates remain high up to 50 nm and decreases slowly as the thickness increases further, which is in agreement with the experimentally observed broad carrier diffusion profile in GaAs 28 . In contrast, the direct near-field excitation of InGaAs and the electron and hole capture rates increases exponentially as the GaAs thickness decreases as seen in Fig.…”

Section: Resultssupporting

confidence: 88%

Active Mediation of Plasmon Enhanced Localized Exciton Generation, Carrier Diffusion and Enhanced Photon Emission

Haq

Addamane

Kafle

et al. 2017

Sci Rep

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Understanding the enhancement of charge carrier generation and their diffusion is imperative for improving the efficiency of optoelectronic devices particularly infrared photodetectors that are less developed than their visible counterpart. Here, using gold nanorods as model plasmonic systems, InAs quantum dots (QDs) embedded in an InGaAs quantum well as an emitter, and GaAs as an active mediator of surface plasmons for enhancing carrier generation and photon emission, the distance dependence of energy transfer and carrier diffusion have been investigated both experimentally and theoretically. Analysis of the QD emission enhancement as a function of distance reveals a Förster radius of 3.85 ± 0.15 nm, a near-field decay length of 4.8 ± 0.1 nm and an effective carrier diffusion length of 64.0 ± 3.0 nm. Theoretical study of the temporal-evolution of the electron-hole occupation number of the excited states of the QDs indicates that the emission enhancement trend is determined by the carrier diffusion and capture rates.Excitons and localized surface plasmons are the two fundamental excitation characteristics of nanoscale materials. The coupling between excitonic and plasmonic materials promises control of photon emission 1-3 and creation of new metamaterial properties 4, 5 that do not exist in nature. Fundamental understanding of exciton-plasmon interaction can lead to development of efficient photovoltaics [6][7][8] , photodetectors 9,10 , photocatalysis 11,12 and other optoelectronic devices. Classic experiments on exciton-plasmon interactions have often used optically transparent spacer materials between the plasmonic metal and excitonic semiconductor materials 1,3,13,14 . Coupling through optically transparent spacers does not allow studying charge transport process. On the other hand, studies on plasmon enhanced near-infrared photo-detectors are focused on coupling metallic two-dimensional-hole-arrays with layered semiconductor materials such as InAs/InGaAs/GaAs dot-in-a-well (DWELL) structures 9,15 . This enhancement mechanism exploits the extraordinary optical transmission effect 16 , where the transmitted field extends to about 1 μm length covering the whole active region 15 , and does not allow fundamental understanding of localized exciton generation, charge carrier diffusion and recombination.In this work, energy transfer and charge carrier diffusion are investigated systematically taking advantage of the tight electric field localization at the interfaces of plasmonic gold nanorods (AuNRs) and semiconductor GaAs that is grown over the InAs/InGaAs DWELL with accurate control of the GaAs thickness. When excitation energy that is above the GaAs band gap is chosen, the localized electric field enhances generation of electron-hole pairs (excitons) in a defined spatial region away from the InAs QDs so that carrier diffusion and capture rates are studied by monitoring the emission intensity of the QDs. The fact that the GaAs thickness can be controlled with sub-nanometer accuracy allows us to study the distanc...

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Section: Resultssupporting

confidence: 88%

Active Mediation of Plasmon Enhanced Localized Exciton Generation, Carrier Diffusion and Enhanced Photon Emission

Haq

Addamane

Kafle

et al. 2017

Sci Rep

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“…In particular, in several cases it has been found to be essential to take into account exciton a) Electronic mail: oliver.brandt@pdi-berlin.de b) Present address: Istituto per la Microelettronica e Microsistemi, Consiglio Nazionale delle Ricerche, via del Fosso del Cavaliere 100, 00133 Roma, Italy formation. [4][5][6][7][8][9][10][11][12][13][14][15] In materials with high exciton binding energies such as diamond, [13][14][15] exciton diffusion may profoundly modify the carrier diffusivity even at elevated temperatures and high carrier densities. Given the exciton binding energy of 26 meV in GaN, we would expect exciton diffusion to play an important role in this material as well.…”

Section: Introductionmentioning

confidence: 99%

Carrier diffusion in GaN -- a cathodoluminescence study. II: Ambipolar vs. exciton diffusion

Brandt,

Kaganer,

Lähnemann

et al. 2020

Preprint

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We determine the diffusion length of excess carriers in GaN by spatially resolved cathodoluminescence spectroscopy utilizing a single quantum well as carrier collector or carrier sink. Monochromatic intensity profiles across the quantum well are recorded for temperatures between 10 and 300 K. A classical diffusion model accounts for the profiles acquired between 120 and 300 K, while for temperatures lower than 120 K, a quantum capture process has to be taken into account in addition. Combining the diffusion length extracted from these profiles and the effective carrier lifetime measured by time-resolved photoluminescence experiments, we deduce the carrier diffusivity as a function of temperature. The experimental values are found to be close to theoretical ones for the ambipolar diffusivity of free carriers limited only by intrinsic phonon scattering. This agreement is shown to be fortuitous. The high diffusivity at low temperatures instead originates from an increasing participation of excitons in the diffusion process.

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“…To prevent measurement artifacts originating from previous excitation pulses [12], the repetition rate is reduced to 4 MHz by a pulse picker (extinction ratio < 1 : 1500). To mitigate spurious influences of lateral carrier diffusion, the laser beam is only moderately focused on the sample surface by a f = 200 mm achromatic lens to a (1/e 2 ) intensity spot diameter of 95 μm, which significantly exceeds the free exciton diffusion length of approximately 10 μm in our sample [28]. For the carrier diffusion coefficient D≈70 cm 2 s −1 [28], the diameter of the Gaussian profile expands only by ≈12% within the first 5 ns after the excitation pulse, during which the carrier energy relaxation and the exciton luminescence rise take place.…”

mentioning

confidence: 99%

“…To mitigate spurious influences of lateral carrier diffusion, the laser beam is only moderately focused on the sample surface by a f = 200 mm achromatic lens to a (1/e 2 ) intensity spot diameter of 95 μm, which significantly exceeds the free exciton diffusion length of approximately 10 μm in our sample [28]. For the carrier diffusion coefficient D≈70 cm 2 s −1 [28], the diameter of the Gaussian profile expands only by ≈12% within the first 5 ns after the excitation pulse, during which the carrier energy relaxation and the exciton luminescence rise take place. The change in carrier density due to diffusive dilution is much weaker than the concurrent reduction of the photocarrier density by radiative recombination.…”

mentioning

confidence: 99%

Thermodynamic origin of the slow free exciton photoluminescence rise in GaAs

et al. 2016

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We use time-resolved photoluminescence (TRPL) spectroscopy to unequivocally clarify the microscopic origin of the nanosecond free exciton photoluminescence rise in GaAs at low temperatures. In crucial distinction from previous work, we examine the TRPL of the GaAs free exciton second LO-phonon replica. This enables us to simultaneously monitor the unambiguous time evolution of the total exciton population and the cooling dynamics of the initially hot free exciton ensemble. We demonstrate by a model based on the Saha equation and the experimentally determined cooling behavior that the long-debated slow photoluminescence rise is caused by time-dependent shifts in the thermodynamic quasiequilibrium between free excitons and the uncorrelated electron-hole plasma.

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Correct determination of low-temperature free-exciton diffusion profiles in GaAs

Cited by 9 publications

References 28 publications

Active Mediation of Plasmon Enhanced Localized Exciton Generation, Carrier Diffusion and Enhanced Photon Emission

Active Mediation of Plasmon Enhanced Localized Exciton Generation, Carrier Diffusion and Enhanced Photon Emission

Carrier diffusion in GaN -- a cathodoluminescence study. II: Ambipolar vs. exciton diffusion

Thermodynamic origin of the slow free exciton photoluminescence rise in GaAs

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