SCREENED COULOMB INTERACTION AND POLARON EXCITON IN AN MIS STRUCTURE

The ground state energy and the binding energy of polaron excitons for med by the minority carriers (holes) bound to electrons in the skin la yer of a metal-insulator-semiconductor structure have been calculated. Allowance is made for the screening of the Coulomb interaction by (a) a gas of free carriers and (b) free carriers in an inversion channel and for the polaron effect. Allowance for the screening of the Coulomb interaction was found to significantly reduce the energy which binds an exciton to the surface, which accounts for an exciton ''dead layer' ' at the surface. The Hamiltonian of electron-phonon interaction with the surface and bulk phonons in which different screening options are taken into account, has been derived.