Band structure and optical properties of strained superlattices

The electronic and optical properties of strained superlattices are considered. A similarity transformation of the strained-superlattice Hamiltonian is presented and the average crystal for this case is defined. A simple perturbative approach to compute the eigenvalues and eigenstates is introduced. The dielectric functions for strained and unstrained superlattices are compared with the two limiting cases, i.e., the corresponding average crystal and the mean value of the bulk constituents' dielectric function. Application is made for the Si/Ge and GaAs/AlAs superlattices.