Fine Tuning of Metal-Insulator Transition in Al<sub>0.3</sub>Ga<sub>0.7</sub>As Using Persistent Photoconductivity

Katsumoto, Shingo; Komori, Fumio; Sano, Naokatsu; Kobayashi, Shun–ichi

doi:10.1143/jpsj.56.2259

Cited by 84 publications

(58 citation statements)

References 9 publications

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“…Even though an accurate absolute measurement of the critical exponent is rather difficult, 25,26 one might hope to detect a change with the BC's. To this end it is not even necessary to open and close the sample.…”

Section: ͑22͒mentioning

confidence: 99%

Boundary conditions, the critical conductance distribution, and one-parameter scaling

Braun¹,

Hofstetter

Montambaux

et al. 2001

Phys. Rev. B

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We study the influence of boundary conditions transverse to the transport direction for disordered mesoscopic conductors both at the Anderson metal-insulator transition and in the metallic regime. We show that the boundary conditions strongly influence the conductance distribution exactly at the metal-insulator transition and we discuss implications for the standard picture of one-parameter scaling. We show in particular that the scaling function that describes the change of conductance with system size depends on the boundary conditions from the metallic regime up to the metal-insulator transition. An experiment is proposed that might test the correctness of the one-parameter scaling theory.

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Section: ͑22͒mentioning

confidence: 99%

Boundary conditions, the critical conductance distribution, and one-parameter scaling

Braun¹,

Hofstetter

Montambaux

et al. 2001

Phys. Rev. B

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“…It was also found that in compensated Al 0.3 Ga 0. 7 As the dielectric constant on the insulating side diverges with the critical exponent of s ≈ 2.3 near the transition, 8 i.e., s ≈ 2ν predicted 12 for the disorder-induced transition holds. Thus there is strong evidence that the effect of disorder rather than electron-electron interaction plays the key role in the MI transition of compensated semiconductors.…”

Section: Introductionmentioning

confidence: 99%

Electrical properties of isotopically enriched neutron-transmutation-doped70Ge:Ganear the metal-insulator transition

et al. 1998

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We report low-temperature carrier transport properties of a series of nominally uncompensated neutron-transmutation-doped 70 Ge:Ga samples very close to the critical concentration Nc for the metal-insulator transition. The nine samples closest to Nc have Ga concentrations N in the range 0.99Nc < N < 1.01Nc. The electrical conductivity σ has been measured in the temperature range T = 0.02 − 1 K. On the metallic side of the transition the standard σ(T ) = a + bT q with q = 1/2 was observed for all the samples except for the two that are closest to Nc with N between Nc and 1.0015Nc. These samples clearly show q = 1/3.An extrapolation technique has been developed in order to obtain the zero-temperature conductivity σ(0) from σ(T ) with different dependence on T . Based on the analysis, ν ≈ 0.5 in the familiar form of σ(0) ∝ (N/Nc − 1) ν has been found. On the insulating side of the transition, variable range hopping resistivity ρ(T ) ∝ exp(T0/T ) p with p = 1/2 has been observed for all the samples having N < 0.991Nc. In this regime T0 ∝ (1 − N/Nc) α with α ≈ 1 as N → Nc. The values of T0 agree very well with theoretical estimates based on the modified Efros and Shklovskii relation kBT0 ≈ (2.8e 2 /4πǫ0κ0ξ0)(1 − N/Nc) α , where κ0 and ξ0 are the dielectric constant and the Bohr radius, respectively. The insulating samples very close to the transition (0.991Nc < N < Nc) exhibit quite a different behavior. In this range 1/p increases rapidly as N changes from 0.991Nc to Nc. The relevance of our findings to the collapsing of the Coulomb gap is discussed.

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“…The first is feasibility of charge-generation from the lightsource. The optical gap of GeSb x Te y is 0.4-0.8 eV [27] allowing inter -band transitions which evidently involve generation of excess charge in the system (note however that effective PPC may be achieved sometimes even for smaller photon energies than necessary for interband transitions [49]). Indium-oxide and other previously studied electron-glasses, tested with the same IRprotocol as in this work, do not meet this requirement.…”

Section: Figmentioning

confidence: 99%

Coexistence of electron-glass phase and persistent photoconductivity in GeSbTe compounds

Ovadyahu

2015

Phys. Rev. B

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It is demonstrated that persistent-photoconductivity (PPC), well-studied in lightly-doped semiconductors, is observable in GeSbTe compounds using infrared excitation at cryogenic temperatures. The low level of energy-flux necessary to induce an appreciable effect seems surprising given the high carrier-concentration n of these ternary alloys (n>10 20 cm -3 ). On the other hand, their high density of carriers makes GeSbTe films favorable candidates for exhibiting intrinsic electron-glass effects with long relaxation times. These are indeed observed in GeSbTe thin-films that are Anderson-localized. In particular, a memory-dip is observed in samples with sheet resistances larger than ≈105 Ω at T≈4K with similar characteristics as in other systems that exhibit intrinsic electron-glass effects. Persistent-photoconductivity however is observable in GeSbTe films even for sheet resistances of the order of 103 Ω, well below the range of disorder required for observing electron-glass effects. These two non-equilibrium phenomena, PPC and electron-glass, are shown to be of different nature in terms of other aspects as well. In particular, their relaxation dynamics is qualitatively different; the excess conductance ∆G associated with PPC decays with time as a stretched exponential whereas a logarithmic relaxation law characterizes ∆G(t) of all electron-glasses studied to date. Surprisingly, the magnitude of the memory-dip is enhanced when the system is in the PPC state. This counter-intuitive result may be related to the compositional disorder in these materials extending over mesoscopic scales. Evidence in support of this scenario is presented and discussed.

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Fine Tuning of Metal-Insulator Transition in Al_0.3Ga_0.7As Using Persistent Photoconductivity

Cited by 84 publications

References 9 publications

Boundary conditions, the critical conductance distribution, and one-parameter scaling

Boundary conditions, the critical conductance distribution, and one-parameter scaling

Electrical properties of isotopically enriched neutron-transmutation-doped70Ge:Ganear the metal-insulator transition

Coexistence of electron-glass phase and persistent photoconductivity in GeSbTe compounds

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Fine Tuning of Metal-Insulator Transition in Al0.3Ga0.7As Using Persistent Photoconductivity

Cited by 84 publications

References 9 publications

Boundary conditions, the critical conductance distribution, and one-parameter scaling

Boundary conditions, the critical conductance distribution, and one-parameter scaling

Electrical properties of isotopically enriched neutron-transmutation-doped70Ge:Ganear the metal-insulator transition

Coexistence of electron-glass phase and persistent photoconductivity in GeSbTe compounds

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Product

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Fine Tuning of Metal-Insulator Transition in Al_0.3Ga_0.7As Using Persistent Photoconductivity