Knight shift in metallic Si: P

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Abstract
For donor densities above the Mott transition, the ratio of Knight shift K P/K Si for 31P and 29Si atoms in Si:P is quantitatively treated for the first time. The electron population at donor sites is estimated from a phenomenological model which employs a linearized Thomas-Fermi calculation of the screening charge in conjunction with previous Kohn-Sham results for the Knight shift in metals. When the ‘depletion’ of electrons in regions between the screened ions is also taken into account, agreement with both the magnitude and donor-density dependence of the experimentally determined K P/K Si is good. It is concluded that the existence of an impurity band at densities above the metal-insulator transition need not be invoked to explain the Knight-shift data, although one may be present.