Low-temperature hopping conduction over the upper Hubbard band in p-GaAs/AlGaAs multilayered structures

Agrinskaya, N. V.; Козуб, В. И.; Ivanov, Yu. L.; Ustinov, V. M.; Chernyaev, A. V.; Шамшур, Д. В.

doi:10.1134/1.1402743

Cited by 13 publications

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“…As a result, the density of states near the Fermi level as a function of energy can be described by interpolation relation as (9) Here max  is the quenching time spent by the system before the application of the magnetic field while min  is the time of the following evolution. However in our case the situation is some more complicated than the one considered in our paper [6].…”

Section: Discussionmentioning

confidence: 99%

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Slow relaxation of magnetoresistance in doped p-GaAs/AlGaAs layers with partially filled upper Hubbard band

Agrinskaya

Козуб

Шамшур

et al. 2009

Solid State Communications

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We observed slow relaxation of magnetoresistance in quantum well structures GaAsAlGaAs with a selective doping of both wells and barrier regions which allowed partial filling of the upper Hubbard band. Such a behavior is explained as related to magnetic-field driven redistribution of the carriers between sites with different occupation numbers due to spin correlation on the doubly occupied centers. Such redistribution, in its turn, leads to slow multi-particle relaxations in -Petersburg, RussiaAbstract We observed slow relaxation of magnetoresistance in quantum well structures GaAs-AlGaAs with a selective doping of both wells and barrier regions which allowed partial filling of the upper Hubbard band. Such a behavior is explained as related to magnetic-field driven redistribution of the carriers between sites with different occupation numbers due to spin correlation on the doubly occupied centers. This redistribution, in its turn, leads to slow multiparticle relaxations in the Coulomb glass formed by the charged centers.

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Section: Discussionmentioning

confidence: 99%

“…The procedure of the fabrication was described in detail in [9]. The middle regions of quantum wells (with thicknesses 5 nm) were doped as well as the middle region of the barriers with the same thicknesses.…”

Section: Methodsmentioning

confidence: 99%

Slow relaxation of magnetoresistance in doped p-GaAs/AlGaAs layers with partially filled upper Hubbard band

Agrinskaya

Козуб

Шамшур

et al. 2009

Solid State Communications

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“…Indeed, the first observation of the effect were reported for In 2 O 3 films. However, recently we have also found the contribution of this mechanism in doped CdTe for samples close to the MIT [12]. The above-mentioned results lead to the conclusion that in many occasions the value of U is smaller than the theoretical estimates.…”

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confidence: 58%

“…It was first demonstrated in Ref. [11] by measurements of magnetophotoconductivity for n-GaAs/AlGaAs multilayered structures and then supported by transport measurements for p-GaAs/AlGaAs structures [12]. Then, as it was noted in [8], the multielectron states in 2D structures can be formed in the wells of the disorder potential.…”

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A Possible Role of the D ^– Band in Hopping Conductivity and Metal–Insulator Transition in 2D Structures

Козуб

2002

phys. stat. sol. (b)

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It is demonstrated that the upper Hubbard band (UHB) can play an important role in the hopping conductivity; 2D geometry and vicinity of the metal-insulator transition emphasize this role. A simple model for the recently observed metal-insulator transition is suggested. The model starts from the insulating limit and implies a principal role of the UHB. It gives a qualitative explanation for most of the features of the transition. The quantitative analysis of MR in the strongly insulating limit leads to values of g-factors in good agreement with the known values.The hopping transport over states within the upper Hubbard band (involving doubly occupied (D À ) localized states) has been considered already in early years of studies of the hopping conductivity [1]. Although the presence of this channel was never disputed, during recent years the hopping was typically considered as related to the "standard" impurity band [2]. It was mainly due to the fact that the theoretical estimate of the binding energy of the doubly occupied state appeared to be too small in comparison to the Bohr energy and the activation to the D À states apparently cannot be discriminated from the activation to the conductance band. This paper is aimed at demonstrating that actually the possibilities to observe a contribution of the upper Hubbard band (UHB) are much better than it has been generally believed. The most favorable situation seems to correspond to the 2D structures. Moreover, we believe that it is a contribution of the D À states which can throw light on the problem of the recently observed metalinsulator transition (MIT) in 2D ([3], see also the review paper [4]). We will describe a simple model starting from the insulating limit which allows to explain the main features of this phenomenon.We start from the nearest neighbor hopping where the contribution of the UHB is associated with the so-called e 2 conductivity. While the temperature dependence of the conductivity does not allow to make a clear conclusion concerning the role of the UHB, the magnetoresistance gives such an opportunity. Indeed, it can be shown that the spin correlations in the D À state lead to an increase of the effective Hubbard energy U (and, correspondingly, of the activation energy e 2 $ U) by the addition [5]As seen, at low temperatures the magnetic field leads to the "universal" addition m B gH which includes the only material parameter --the g-factor. Basing on these considerations, we have reconsidered the existing data on the magnetoresistance for the nearest neighbor hopping in recent papers [5,6]. The surprisingly good agreement between the g-factor values extracted from the experimental data and the corresponding handbook values leads us to the conclusion that in many cases the magnetoresistance is related to phys. stat. sol. (b) 230,

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“…Study of the hopping conductivity at low temperatures allowed to determine the radius of an A þ center. 11,12 Photoluminescence measurements carried out in the same samples have shown the presence of a new line in the spectra, associated with the transition of photoexcited electrons to an A þ center. 13 In the present paper we describe the results of the work that has been carried out by us for the last ten years and has been devoted to the study of the optical properties of A þ centers in GaAs/AlGaAs quantum wells.…”

Section: A 1 and D 2 Centers In Quantum Wellsmentioning

confidence: 95%

Spin and charge effects due to positively charged acceptors in GaAs/AlGaAs quantum wells

Petrov

Ivanov

Аверкиев

2015

Low Temperature Physics

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Articles you may be interested inEnergy dependence of electron effective mass and effect of wave function confinement in a nanoscale In0.53Ga0.47As/In0.52Al0.48As quantum well Softening of the tunneling gap in modulation-doped GaAs/AlGaAs asymmetric coupled double quantum wells in magnetic fields Appl. Phys. Lett. 95, 082102 (2009); 10.1063/1.3213352 Optical coherent transient effects in magnetoactive GaAs/AlGaAs quantum well structure J. Appl. Phys. 95, 4833 (2004); 10.1063/1.1697621 Charge transfer of carriers by interband photoexcitation in asymmetric GaAs/AlGaAs coupled quantum wells Appl. Phys. Lett. 78, 2879 (2001); 10.1063/1.1369413In-plane magnetophotoluminescence studies of modulation-doped GaAs/AlGaAs coupled double quantum wellsWe present the results of optical measurements on the structures containing GaAs/AlGaAs quantum wells with positively charged acceptors (A þ centers). The data on the spin structure and localization of the A þ centers in the 2D system were obtained using magneto-optical measurements. The energy structure of the A þ impurity band was studied using the temperature dependence of photoluminescence. Based on the analysis of the complete set of experimental data obtained by different optical methods and their comparison with the results of transport measurements reported in literature, we developed a unified physical picture of charge and spin phenomena in such systems. A new experimental method, based on the measurements of photoexcitation and photoluminescence spectra, is proposed for studies of the Coulomb gap appearing at low temperatures in the density of localized states. V C 2015 AIP Publishing LLC. [http://dx.

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Low-temperature hopping conduction over the upper Hubbard band in p-GaAs/AlGaAs multilayered structures

Cited by 13 publications

References 9 publications

Slow relaxation of magnetoresistance in doped p-GaAs/AlGaAs layers with partially filled upper Hubbard band

Slow relaxation of magnetoresistance in doped p-GaAs/AlGaAs layers with partially filled upper Hubbard band

A Possible Role of the D ^– Band in Hopping Conductivity and Metal–Insulator Transition in 2D Structures

Spin and charge effects due to positively charged acceptors in GaAs/AlGaAs quantum wells

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Low-temperature hopping conduction over the upper Hubbard band in p-GaAs/AlGaAs multilayered structures

Cited by 13 publications

References 9 publications

Slow relaxation of magnetoresistance in doped p-GaAs/AlGaAs layers with partially filled upper Hubbard band

Slow relaxation of magnetoresistance in doped p-GaAs/AlGaAs layers with partially filled upper Hubbard band

A Possible Role of the D – Band in Hopping Conductivity and Metal–Insulator Transition in 2D Structures

Spin and charge effects due to positively charged acceptors in GaAs/AlGaAs quantum wells

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A Possible Role of the D ^– Band in Hopping Conductivity and Metal–Insulator Transition in 2D Structures