VARIATIONAL CALCULATIONS FOR SEMICONDUCTOR SUPERLATTICES AND MULTILAYER SYSTEMS

We have developed a variational multicomponent hypernetted-chain theory for calculation of the elementary collective excitations in semiconductor superlattices. The infinite lattices are mapped onto multicomponent systems with a Bloch-sum type of transformation. The finite multilayer systems can also be treated as a straightforward extension of the multicomponent fluid theory. Numerical results are presented for both finite and infinite type-I lattices. Some simple analytic results that go beyond the random-phase approximation and self-consistent-field approximation are also presented for type-II and polytype systems. Numerical results for pressure and bulk modulus in electron-electron and electron-hole two-layer systems primarily indicate the region of stability of these systems with respect to electron density and interlayer separation.