Electrical characteristics of heavily doped NTD Ge at very low temperatures

We report about the measurement of the electric characteristics of some NTD Ge thermistors at temperatures down to 25 mK. The dopant concentration is around 6×1016cm-3, producing a material of characteristics close to the metal-to-insulator transition. Fitting the ρ(T) characteristics with a variable exponent p Mott's law, a p around 0.6 was obtained. This result confirms the hypothesis of a dependence of p on the doping level.