Heavily Doped Semiconductors: Magnetic Moments, Electron-Electron Interactions and the MetalInsulator Transition

Abstract

Electron localization in a metal, ultimately leading to a metal-insulator transition (MIT), can occur because of disorder (Anderson transition) or electron-electron interactions (Mott-Hubbard transition). Both effects play a role in heavily doped semiconductors which have become prototype systems for the study of MIT. In this review we focus on phosphorus-doped Si. The MIT in Si:P can be tuned by varying the P concentration or — for barely insulating samples — by application of uniaxial stress S. The continuous stress tuning allows the observation of dynamic scaling of σ(T, S) and hence a reliable determination of the critical exponent μ of the extrapolated zerotemperature conductivity σ(0) ~∣ S — S c ∣μ, i.e. μ = 1, and of the dynamical exponent z = 3.