Evidence for ɛ 2-conductivity in the magnetoresistance of multivalley semiconductors

Agrinskaya, N. V.; Козуб, В. И.; Polyanskaya, T. A.; Saidov, A. S.

doi:10.1134/1.1187659

Cited by 6 publications

(5 citation statements)

References 9 publications

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“…Thus, the inherently bounded temperature regime that could be pertinent to the E 2 -conduction mechanism will be squeezed. Previously, the E 2 -conduction process has only been found in very carefully doped as well as compensated semiconductors Ge [31][32][33], CdTe [34], GaAs [35], GaInP 2 [36,37], and Ge:Sb [38].…”

Section: Semiconducting Zno Nanowiresmentioning

confidence: 99%

Electrical conduction mechanisms in natively doped ZnO nanowires

Chiu

Lin

2008

Nanotechnology

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Single-crystalline zinc oxide (ZnO) nanowires (NWs) with diameters of 90-200 nm were synthesized by the thermal evaporation method. Four-probe Ti/Au electrodes were made by the standard electron-beam lithography technique, and the intrinsic resistivities, rho(T), of individual NWs were measured over a wide range of temperature from 300 down to 0.25 K. The temperature behavior of rho(T) between 300 and 5 K reveals that the intrinsic electrical-transport mechanisms through individual ZnO NWs are due to a combination of the thermal activation conduction and the nearest-neighbor hopping conduction processes. Three distinct activation and hopping contributions with discrete characteristic activation energies are observed. Above about 100 K, the charge transport mechanism is dominated by the thermal activation of electrons from the Fermi level, mu, to the conduction band. Between approximately 20 and 100 K, the charge transport mechanism is due to the activation of electrons from mu to the upper impurity (D-) band. Between approximately 5 and 20 K, the charge transport mechanism arises from the nearest-neighbor hopping conduction within the lower impurity (D) band. Such unique electrical conduction behaviors can be explained in terms of the intricate material properties (in particular, the presence of moderately high concentrations of n-type defects accompanied with a slight self-compensation) in natively doped ZnO NWs. In one heavily doped NW, a surface-related conduction process manifesting the two-dimensional attributes of quantum-interference transport phenomena is observed. The carrier concentrations in our NWs have been estimated, and they were found to lie close to the critical concentration for the Mott metal-insulator transition.

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Section: Semiconducting Zno Nanowiresmentioning

confidence: 99%

Electrical conduction mechanisms in natively doped ZnO nanowires

Chiu

Lin

2008

Nanotechnology

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“…However the existing experimental estimates of the activation energies for ε 2 nearestneighbor hopping conductivity give values much less than theoretical estimates (about 10 meV) -as small as to say 1 meV and even smaller (see e.g. [2] and references given in this paper and also [10]). The most reliable of these estimates were based on studies of magnetoresistance which give a unique possibility to reveal the D − band contribution.…”

Section: The Modelmentioning

confidence: 61%

“…In recent papers [1,2], the existing data on the hopping magnetoresistance for the nearest neighbor hopping were reconsidered with a conclusion that in many cases the magnetoresistance is related to a suppression of a contribution of the upper Hubbard band due to a spin alignment. A signature of such a behavior is a universal magnetic field behavior of the activation energy related to the Zeeman splitting.…”

Section: Introductionmentioning

confidence: 99%

“…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.…”

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confidence: 99%

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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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“…Anomal positive magnetoresistance takes place in heavily doped semiconductors in the hopping conductance range at low temperatures and corresponds to localization on impurity of two charge carriers with parallel spins [17]. Application of a magnetic field leads to a particular orientation of spins carriers, through which they are removed from the transfer process.…”

Section: Part B: Magnetotransport Properties Of Heavily Doped Si Whismentioning

confidence: 99%

Magnetic susceptibility and magnetoresistance of neutron-irradiated doped SI whiskers

Druzhinin

Ostrovskii

Khoverko

et al. 2015

Journal of Magnetism and Magnetic Materials

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Evidence for ɛ 2-conductivity in the magnetoresistance of multivalley semiconductors

Cited by 6 publications

References 9 publications

Electrical conduction mechanisms in natively doped ZnO nanowires

Electrical conduction mechanisms in natively doped ZnO nanowires

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

Magnetic susceptibility and magnetoresistance of neutron-irradiated doped SI whiskers

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Evidence for ɛ 2-conductivity in the magnetoresistance of multivalley semiconductors

Cited by 6 publications

References 9 publications

Electrical conduction mechanisms in natively doped ZnO nanowires

Electrical conduction mechanisms in natively doped ZnO nanowires

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

Magnetic susceptibility and magnetoresistance of neutron-irradiated doped SI whiskers

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