Geometrical magnetoresistance and hall mobility in gunn effect devices

Jervis, T. R.; Johnson, Evan

doi:10.1016/0038-1101(70)90049-3

Cited by 70 publications

(38 citation statements)

References 7 publications

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“…2 [26]. While the two mobilities agree very well in the larger gate voltage region above the kink, they are distinct from each other in the transition region (Fig.…”

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confidence: 72%

Tuning of Metal–Insulator Transition of Quasi-Two-Dimensional Electrons at Parylene/SrTiO₃ Interface by Electric Field

et al. 2009

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Electrostatic carrier doping using a field-effect-transistor structure is an intriguing approach to explore electronic phases by critical control of carrier concentration [1,2]. We demonstrate the reversible control of the insulator-metal transition (IMT) in a two dimensional (2D) electron gas at the interface of insulating SrTiO3 single crystals. Superconductivity was observed in a limited number of devices doped far beyond the IMT, which may imply the presence of 2D metal-superconductor transition. This realization of a two-dimensional metallic state on the most widely-used perovskite oxide is the best manifestation of the potential of oxide electronics.The perovskite SrTiO 3 is sometimes called the "silicon of oxide electronics" because it is commonly used as a substrate for epitaxial growth of a variety of oxide films [3]. Not only it is an insulator with a band gap of 3.2 eV but also a quantum paraelectric with an extremely large dielectric constant of more than 10 6 at low temperatures [4]. N-type conduction has been realized by introducing a small number of oxygen vacancies or by cation substitutions. An insulator to metal transition occurs at a rather low carrier concentration of n ∼1018 cm −3 [5, 6] for a doped oxide system, which owes largely to the high mobility exceeding 10 4 cm 2 /Vs. Superconductivity emerges in a limited concentration range from n = 7 × 10 18 to 5 × 10 20 cm −3 and the transition temperature T c shows a bell shaped dependence on n with an optimum T c ∼ 0.35 K at n ∼ 10 20 cm −3 [7]. The carrier concentration required to achieve superconductivity is two orders of magnitude smaller than that for high-T c cuprates which is a great advantage to realize electrostatic control of insulator-metal and superconductor transitions.Such a unique doping properties of SrTiO 3 has triggered attempts to dope charged carriers electrostatically by using a field effect transistor (FET) structure. However, so far, attempts to realize metallic state have been unsuccessful [8]. This is due to several reasons, notably carrier trapping at the gate insulator/SrTiO 3 interface, Schottky barrier formation between SrTiO 3 and source and drain electrodes, and insufficient breakdown voltage of the gate insulators. An alternative approach has shown that two dimensional electron gas can be created at SrTiO 3 /LaAlO 3 hetero-interface by a charge-transfer due to a polar discontinuity [9,10,11,12,13,14] or possible oxygen defects [15]. This electronically tailored interface was found to be superconducting as in the bulk material [14].Recently the performance of SrTiO 3 FET has been drastically improved [16,17] by overcoming the contacts and interface problems. These new devices showed metallic behavior down to 7 K [17]. In this Letter, we extend our study to lower temperatures below 1 K, and show that the two-dimensional insulator-metal transition is indeed achieved at the interface between parylene and SrTiO 3 reversibly while sweeping the gate voltage. A superconducting transition to zero-resistance state was obs...

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“…2 [26]. While the two mobilities agree very well in the larger gate voltage region above the kink, they are distinct from each other in the transition region (Fig.…”

mentioning

confidence: 72%

Tuning of Metal–Insulator Transition of Quasi-Two-Dimensional Electrons at Parylene/SrTiO₃ Interface by Electric Field

et al. 2009

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“…Geometric magnetoresistance (GMR) measurements provide a useful technique to determine the electron mobility in barrier-structure samples of mesa geometry [2,8,9,[22][23][24]. In this technique, a steady magnetic field (B) is applied to the sample parallel to the layers but perpendicular to the vertical current.…”

Section: Geometric Magnetoresistance Measurementsmentioning

confidence: 99%

“…Brought to you by | MIT Libraries Authenticated Download Date | 5/9/18 11:58 AM is the magnetoresistance, and µ GMR is the GMR mobility, which is usually taken approximately equal to the Hall mobility [2,4,8,9,[22][23][24]. In order to use the GMR technique, the magnetic field must be low enough to ensure that (µ GMR B) 2 1, and the mesa diameter ( ) must be much greater than the total thickness (L) of the barrier layers [4,8,23].…”

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confidence: 99%

Temperature and electric field dependences of the mobility of electrons in vertical transport in GaAs/Ga1−y AlyAs barrier structures containing quantum wells

2008

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The mobility of electrons in vertical transport in GaAs/Ga1−y AlyAs barrier structures was investigated using geometric magnetoresistance measurements in the dark. The samples studied had Ga1−y AlyAs (0 ≤ y ≤ 0:26) linearly graded barriers between the n+-GaAs contacts and the Ga0:74Al0:26As central barrier, which contain N w (=0, 2, 4, 7 and 10) n-doped GaAs quantum wells. The mobility was determined as functions of (i) temperature (80–290 K) at low applied voltage (0.01–0.1 V) and (ii) applied voltage (0.005–1.6 V) at selected temperatures in the range 3.5–290 K. The experimental results for the temperature dependence of low-field mobility suggest that space-charge scattering is dominant in the samples with N w=0 and 2, whereas ionized impurity scattering is dominant in the samples with N w=4, 7 and 10. The effect of polar optical phonon scattering on the mobility becomes significant in all barrier structures at temperatures above about 200 K. The difference between the measured mobility and the calculated total mobility in the samples with N w=4, 7 and 10, observed above 200 K, is attributed to the reflection of electrons from well-barrier interfaces in the quantum wells and interface roughness scattering. The rapid decrease of mobility with applied voltage at high voltages is explained by intervalley scattering of hot electrons.

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“…First, the physical magnetoresistance effect (PMR) is related to conduction-process anisotropy, multi-carrier-type conduction, and energy-dependent carrier scattering. [1,2] If the sample is a long, thin rectangular bar with an applied transverse magnetic field, Lorentz forces on the carriers are balanced by the Hall electric field developed across the bar. PMR occurs when carriers with energy above and below the average energy are under-and over-compensated by this Hall field and result in increased resistivity.…”

Section: Introductionmentioning

confidence: 99%

“…This effect is geomagnetoresistance (GMR), and it can be a much larger effect than PMR. [2] Long, rectangular samples with contacts at the ends of the long sample have a large length-to-width ratio (L/W), and the magnetoresistance effect is very small. [1] As L/W approaches zero, as it is for the Corbino disk, the magnetoresistance effect increases.…”

Section: Introductionmentioning

confidence: 99%

Magnetoresistance technique for determining cross-plane mobility in superlattice devices

Johnston

Ahrenkiel²,

Young³

et al.

Eighteenth International Conference on Thermoelectrics. Proceedings, ICT'99 (Cat. No.99TH8407)

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The cross-plane mobility, in the direction perpendicular to the planes of a superlattice, is critical for the computation of the figure of merit (ZT) in a thermoelectric device. The measurement of cross-plane mobilities in thermoelectric superlattice structures cannot be performed by conventional techniques such as the van der Pauw method. Therefore, alternative techniques must be used to obtain this important parameter. Magnetoresistance is the increase in material resistivity due to a lengthened path for charge carriers in a perpendicular magnetic field. The magnetoresistance is related to the magnetic field strength as (µB) 2 in the standard configuration, but the field dependence is also influenced by device geometry. This work focuses on measuring superlattice samples of composition Bi 2 Te 3 /Sb 2 Te 3 that are removed from their growth substrate and mounted on metal-coated substrates. This resulting mesa structure has a 100-µm-square contact metallization. Technical issues related to the sample preparation for the measurement are discussed. The magnetoresistance effect is expected to be small due to the anticipated low mobilities in Bi 2 Te 3 -based materials. Magnetoresistance studies with such superlattice thermo-elements were attempted using a dc magnetic field, but the sensitivity was insufficient. An ac magnetoresistance with lock-in detection can yield improved sensitivity. IntroductionMagnetoresistance is the increase in sample resistance due to the presence of a magnetic field. It may be useful for determining mobility when the sample structure does not permit van der Pauw contacts typically used for Hall-effect mobility measurements. The increased resistance induced by an applied magnetic field is due to both resistivity changes in the semiconductor sample and geometrical effects. First, the physical magnetoresistance effect (PMR) is related to conduction-process anisotropy, multi-carrier-type conduction, and energy-dependent carrier scattering. [1,2] If the sample is a long, thin rectangular bar with an applied transverse magnetic field, Lorentz forces on the carriers are balanced by the Hall electric field developed across the bar. PMR occurs when carriers with energy above and below the average energy are under-and over-compensated by this Hall field and result in increased resistivity.[2] If the sample consists of a thin plate with metallic contacts on the large faces, then the Hall field due to the transverse magnetic field would effectively be shorted out by the contacts. With no Hall field, the current flows at the Hall angle and magnetoresistance is observed even with no PMR. This effect is geomagnetoresistance (GMR), and it can be a much larger effect than PMR. [2] Long, rectangular samples with contacts at the ends of the long sample have a large length-to-width ratio (L/W), and the magnetoresistance effect is very small. [1] As L/W approaches zero, as it is for the Corbino disk, the magnetoresistance effect increases.[1] The resistance ratio of sample resistance in a magnetic f...

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Geometrical magnetoresistance and hall mobility in gunn effect devices

Cited by 70 publications

References 7 publications

Tuning of Metal–Insulator Transition of Quasi-Two-Dimensional Electrons at Parylene/SrTiO₃ Interface by Electric Field

Tuning of Metal–Insulator Transition of Quasi-Two-Dimensional Electrons at Parylene/SrTiO₃ Interface by Electric Field

Temperature and electric field dependences of the mobility of electrons in vertical transport in GaAs/Ga1−y AlyAs barrier structures containing quantum wells

Magnetoresistance technique for determining cross-plane mobility in superlattice devices

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Geometrical magnetoresistance and hall mobility in gunn effect devices

Cited by 70 publications

References 7 publications

Tuning of Metal–Insulator Transition of Quasi-Two-Dimensional Electrons at Parylene/SrTiO3 Interface by Electric Field

Tuning of Metal–Insulator Transition of Quasi-Two-Dimensional Electrons at Parylene/SrTiO3 Interface by Electric Field

Temperature and electric field dependences of the mobility of electrons in vertical transport in GaAs/Ga1−y AlyAs barrier structures containing quantum wells

Magnetoresistance technique for determining cross-plane mobility in superlattice devices

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Tuning of Metal–Insulator Transition of Quasi-Two-Dimensional Electrons at Parylene/SrTiO₃ Interface by Electric Field

Tuning of Metal–Insulator Transition of Quasi-Two-Dimensional Electrons at Parylene/SrTiO₃ Interface by Electric Field