The temperature dependence of variable range hopping resistivity ρ in neutron transmutation doped (NTD) isotopically enriched70Ge:Ga samples is reported. Five samples with compensation ratios K less than 0.001 and Ga concentrations between 3×1016 and 1.77×1017 cm-3 were studied. All samples investigated show the ln ρ∝T-1/2 dependence in the temperature range below 1.5K. As thermistor materials NTD70Ge:Ga samples are found to have more than factor of two higher sensitivity than commonly used natural NTD Ge in the temperature range between 0.2K and 1K. Our results are compared with theoretical predictions for variable range hopping conduction.
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