Scattering of holes of a two-dimensional gas near Germanium surfaces cleaved in liquid Nitrogen

Hall measurements were made to determine the mobility and concentration of holes in the inversion channels near the surfaces of n-type Ge samples cleaved in liquid nitrogen having different donor concentrations. The experimental results obtained agree with the theory of the scattering of a two-dimensional hole gas by Coulomb centres. The comparison of theory and experiment gives reason to the conclusion that the structure of the valence band near the surface immediately after cleavage is essentially different from the structure in the bulk. The dependence of the charge in the surface levels Qss upon the donor concentration in the bulk, Nd, is found to have the form Qss ∼ Nd1/3.