Electronic, optical, and lattice properties of superlattices and heterostructures

Using an envelope function model, we have calculated the valence band structures in quantum wells and superlattices. It is found that the valence bands exhibit very complicated structures. With the newly devised method and the aid of the CRAY supercomputer, we have been able to calculate the optical absorption spectra for a number of GaAs-Ga$\sb{1-x}$Al$\sb{x}$As superlattices and quantum wells with the valence band mixing included. The results which feature the saddle point exciton resonances in superlattices are in good agreement with the experimental data.The continuum model (recently confirmed by microscopic calculations) shows that, for GaAs-AlAs superlattices, there exist a number of interface and angle-dependent long-wavelength optical modes. To better understand these properties, we developed a simple microscopic model which helps understand these novel features both qualitatively and quantitatively. This also enables us to obtain the phonon-polariton dispersion curves in superlattices with spatial dispersion included.U of I OnlyETDs are only available to UIUC Users without author permissio