We investigated four series of Ge samples of isotopic mixtures of 74Ge and 70Ge doped by the neutron transmutation doping technique with a compensation degree K = 1.4, 12, 38 and 54% and n-type conductivity which show a strong dependence of the critical impurity concentration Nc on K. For barely insulating samples we determined the critical scaling exponents of the localization length and of the dielectric constant by analysis of the temperature dependence of hopping resistance and of the positive magnetoresistance at variable range hopping with Coulomb gap. For low disorder (K = 1.4 and 12%) the critical exponents of the localization length and the dielectric constant are v = 0.66 ± 0.27 and ζ = 1.07 ± 0.27, which nearly double for medium disorder (K = 38 and 54%) to v = 1.59 ± 0.32 and ζ = 1.94 ± 0.2, respectively.
|Number of pages||4|
|Journal||Physica Status Solidi (B): Basic Research|
|State||Published - Mar 2000|