Andrei Georgievich Zabrodskii

Coulomb gap, its critical behavior, and the metal-insulator transition in doped semiconductors

To measure a density of localized states in the vicinity of the Fermi level variable range hopping spectroscopy procedure has been established. As a result the parabolic Coulomb gap has been discovered on a set of the series of doped and compensated semiconductors. The gap has a single- or multielectron origin for the case of strong localization when a compensation degree is close to unity or moderate correspondingly. All the gaps turned out to be collapsing in the critical point for the metal-insulator transition. One can consider the transition as Coulomb gap collapsing phenomenon in a frame of the scaling theory describing it as a second order phase transition. The critical indices for a localization radius and for a metallic conductivity are nearly equal to unity.