Semiconductor-to-Metal Transition in $n$-Type Group IV Semiconductors

A synthesis is given of the most significant experimental features of the semiconductor-to-metal transition in group IV semiconductors. Two characteristic concentrations are discussed, the first being for a delocalization of electrons (the "Mott" transition), and the second being associated with the entry of the Fermi level into the conduction band of the host material. Experimental values are given for the two concentrations in several materials. Experimental data covering measurements of Hall coefficient, electrical resistivity and carrier mobility, NMR properties, magnetoresistance, magnetic susceptibility, and ESR properties are employed in arriving at values for the two characteristic concentrations. Si: P is taken as the model system because of the completeness of experimental measurements. Si: As is also briefly considered. Existing data for $n$-Ge are examined, as well as the more restricted evidence concerning $n$-SiC.