OBSERVATION OF CORRELATION GAP IN QUASI-2D IMPURITY BAND OF SI-B MOS STRUCTURE

We studied longitudinal conductivity sigma of Si:B (N-B approximate to 10(18)cm(-3)) MOS-structures with doped layer thickness 0.5 mu, scann ing Fermi energy through valence and impurity bands with gate voltage V-g. The quasi-2D channel, responsible for conductivity in such struct ures, is formed in the region where the Fermi level crosses the impuri ty band, shifted by V-g. We have observed two minima in the sigma(V-g) dependence. The first one, which is due to the gap between extended a nd localized impurity states, is observed in the temperature range stu died (4.2-30K), while the second one - only at low enough temperatures (<6K) and assumed to be associated with correlation effects, leading to selfconsistent redistribution of electron density.