ELECTRONIC SUPERSTRUCTURES IN DOPED SUPERLATTICES

Using an approach based on the density functional, we show that the ex change-correlation contribution to the system energy can be bigger tha n the sum of the kinetic energy and the Hartree contribution due to re distribution of carriers over the quantum wells in doped composite sup erlattices at low temperatures and moderate impurity densities. As a r esult, the ground state of the system can correspond to an inhomogeneo us electron distribution over the quantum wells. Conditions when the h omogeneous state is stable against small and finite density fluctuatio ns are determined, and a phase diagram is plotted. A nonlinear theory of the inhomogeneous state is considered. (C) 1998 American Institute of Physics. [S1063-7761(98)02309-9].