Study of electrical properties in the insulating samples 70Ge: Ga p-type at very low temperatures

Experimental results on resistivity of the insulating samples 70Ge: Ga p-type at low temperatures has been analyzed in the insulating side of the Metal-Insulator Transition (MIT). The resistivity measurements were obtained in the temperature range 0.05-2.7 K. The five samples studied have Ga concentrations n ranging from 0.302 × 1017 to 1.84 × 1017 cm−3. On the insulating side of the MIT, the study of the effect of low temperatures T on the electrical transport shows that the temperature dependence of the electrical conductivity is found to follow the Efros-Shklovskii Variable Range Hopping regime with T−1/2. This behavior showed that long range electron-electron interaction reduces the Density Of State of carriers at the Fermi level and creates the Coulomb gap. The data are for a 70Ge:Ga sample prepared and reported by Itoh et al. [22] .