Chemical equilibrium between excitons, electrons, and negatively charged excitons in semiconductor quantum wells

Siviniant, J.; Scalbert, D.; Kavokin, Alexey; Coquillat, Dominique; Lascaray, J. P.

doi:10.1103/physrevb.59.1602

Cited by 76 publications

(83 citation statements)

References 7 publications

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“…Negatively charged excitons in asymmetric double QW structures have been already observed by Siviniant et al [2]. In that case, the electron population originated from different tunneling rates for electrons and holes from one QW to the other.…”

Section: Resultsmentioning

confidence: 65%

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Exciton and Charged Exciton Absorption in Asymmetric Double Quantum Well Structures

opotowski

ski

kowski

et al. 2002

phys. stat. sol. (a)

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We present absorption studies of neutral and negatively charged excitons in nominally undoped CdTe-based asymmetric double quantum well structure. The origin of excess electron concentration is shown to be related to hole trapping by deep centers. An additional illumination with sapphire laser is used to change excess electron concentration in the well. We apply a phenomenological model to extract transition intensities and energies. The dependence of the dissociation energy on electron concentration is roughly linear. The extrapolation of dissociation energy to zero concentration yields a value of 3.8 meV.Introduction Since its first experimental observation in quantum wells (QWs) [1], charged excitons (trions) -excitonic complexes consisting of an exciton with an additional electron or hole bound to it -have attracted a growing interest. They have been observed in systems with excess carriers generated by various mechanisms. The most obvious one is modulation doping. Other techniques utilize different electron and hole tunneling rates from either another QW [2] or a superlattice [3] to produce a net concentration of carriers. Negatively charged excitons have also been observed in QWs where neither of the above cases take place [4]. In such case, the authors claim that the excess carriers originate from the transfer of electrons from ionized acceptor impurities in the barrier to the QW. In this work, we present absorption studies of charged excitons in nominally undoped asymmetric double QW structure. We show that the generation mechanism of excess carriers is not connected with carrier tunneling from one QW to another, but rather with the existence of a deep center acting as a hole trap, which can be depopulated by additional illumination.

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Section: Resultsmentioning

confidence: 65%

“…The most obvious one is modulation doping. Other techniques utilize different electron and hole tunneling rates from either another QW [2] or a superlattice [3] to produce a net concentration of carriers. Negatively charged excitons have also been observed in QWs where neither of the above cases take place [4].…”

mentioning

confidence: 99%

Exciton and Charged Exciton Absorption in Asymmetric Double Quantum Well Structures

opotowski

ski

kowski

et al. 2002

phys. stat. sol. (a)

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“…It was also previously shown that the carrier diffusion, and thus the carrier accumulation in the quantum wells leading to a charged exciton formation in double well systems, is strongly dependent on the excitation energy. 4 The formation of biexcitons at an excitation density of 6 mW/cm 2 disagrees with the density dependence measured for nearly resonant excitation in comparable quantum wells, 6 finding an onset of biexciton formation at 1 KW/cm 2 . Instead, the formation of optically induced charged excitons is observed at low excitation intensities, since the background carrier density is proportional to the tunneling or thermal escape time of the spatially separated carriers, which can be much longer than the exciton-recombination time relevant for the exciton density.…”

Section: ͓S0003-6951͑99͒05040-8͔mentioning

confidence: 70%

“…Charged excitons with binding energies comparable to biexcitons are reported for a variety of different quantum well structures like AlGaAs 2,3 and CdMnTe. 4,5 In Ref. 1 the strong wavelength-dependent formation of the sideline was attributed to a reduced carrier temperature at more resonant excitation.…”

Section: ͓S0003-6951͑99͒05040-8͔mentioning

confidence: 99%

Comment on “High efficient biexciton photoluminescence observed from single ZnCdSe quantum wells with continuous wave cold carrier generation” [Appl. Phys. Lett. 74, 1138 (1999)]

Langbein

1999

Applied Physics Letters

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“…With increasing n e the number of trions increases, as is expected and which is experimentally observed. 28,29,35 For n e ϭ2ϫ10 10 cm…”

Section: Resultsmentioning

confidence: 99%

Dynamical equilibrium between excitons and trions in CdTe quantum wells in high magnetic fields

et al. 2002

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The formation of two-dimensional negatively charged excitons ͑negative trions͒ out of excitons and free electrons is found to be determined by a dynamical equilibrium. This dynamical equilibrium consists of a chemical equilibrium, relating the trion, exciton, and electron populations, modified by finite formation and recombination times of ͑charged͒ excitons, as is evidenced by a magnetic-field-dependent photoluminescence ͑PL͒ and far-infrared study of doped CdTe/CdMgTe quantum wells. The data show that the trion formation is entirely driven by the occupation of the spin-split trion, exciton and electron levels. Incorporation of the proposed trion formation scheme into a rate equation model gives a proper description of the experimental data, leading to values of the formation, recombination, and spin-flip times of trions and excitons that are in good agreement with results of time-resolved experiments in the literature. The model elucidates the effect of the heavy-hole splitting on the polarization degree of the trion PL in a magnetic field and the influence of the dark excitons on the trion formation.

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Chemical equilibrium between excitons, electrons, and negatively charged excitons in semiconductor quantum wells

Cited by 76 publications

References 7 publications

Exciton and Charged Exciton Absorption in Asymmetric Double Quantum Well Structures

Exciton and Charged Exciton Absorption in Asymmetric Double Quantum Well Structures

Comment on “High efficient biexciton photoluminescence observed from single ZnCdSe quantum wells with continuous wave cold carrier generation” [Appl. Phys. Lett. 74, 1138 (1999)]

Dynamical equilibrium between excitons and trions in CdTe quantum wells in high magnetic fields

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