State of Mott minimal metallic conductivity in a scaling approach to the metal-insulator transition in doped semiconductors

We show that the temperature-independent conductivity on the metallic side of the metal-insulator transition in doped Ge and Si can be associated with the value of Mott minimal metallic conductivity sigma(M) = C(e(2)/h)Ni-c(1 /3). The numerical coefficient C approximate to 0.06 for p-Ge and p-Si is i n agreement with the value predicted by Mott (0.04-0.08), while C approxima te to 0.12 for n-Ge and n-Si. The obtained values of sigma(M) normalize the scaling behavior of the zero-temperature conductivity sigma(0), so that th e dimensionless conductivity sigma(0)sigma(M) for different impurity system s merge into a single dependence for,l-Ge and n-Si. [S0163-1829(98)07148-3] .