Electron-electron interactions and the metal-insulator transition in heavily doped silicon

The metal-insulator (MI) transition in Si:P can be tuned by varying the P concentration or - for barely insulating samples - by application of uniaxial stress S. On-site Coulomb interactions lead to the formation of localized magnetic moments and the Kondo effect on the metallic side, and to a Hubbard splitting of the donor band on the insulating side. Continuous stress tuning allows the observation of finite-temperature dynamic scaling of sigma(T, S) and hence a reliable determination of the critical exponent mu of the extrapolated zero-temperature conductivity sigma(0) similar to vertical bar S - S-c vertical bar(mu), i.e., mu = 1, and of the dynamical exponent z = 3. The issue of half-filling vs. away from half-filling of the donor band (i.e., uncompensated vs. compensated semiconductors) is discussed in detail. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim