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The Scaling Behaviour of the Metal-Insulator Transition of Isotopically Engineered Neutron-Transmutation Doped Germanium

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1998

Year

Abstract

We measured on the dielectric side, with |N/Nc — 1| ≤ 0.64 the critical indices of the metal–insulator transition (MIT) in n-Ge with low (1.4 and 12%) and medium (38 and 54%) compensation, prepared by neutron-transmutation doping (NTD) of isotopic mixtures of 74Ge and 70Ge. We analyzed from the temperature dependence of hopping resistance in the variable-range hopping (VRH) regime with Coulomb gap the scaling of the localization length a, and of the dielectric constant ϰ. At low compensation we find that the critical indices are ν ≈︂ 1/2, ζ ≈︂ 1, which increase up to ν ≈︂ 1, ζ ≈︂ 2, for medium compensations.