Many-body effects in type II heterostructures

A theoretical description of large optical nonlinearities in type II heterostructures was derived. The electronic states in such structures confine the electrons and holes in spatially separate layers. The interband absorption of the GaAs layer in the presence of a quasi-equilibrium hole plasma was calculated. This involves solving the Bethe-Salpeter equation containing dynamic screening of the Coulomb potential, the corresponding Hartree-Fock self-energies, and phase-space filling. The calculated absorption spectra show a large blue shift and bleaching of the heavy-hole exciton in agreement with recent experimental results. Combining the space charge shifts with the many-body bandgap renormalization, the shift in the photoluminescence energy associated with the type II recombination was calculated. Depending on the structure, the luminescence energy can shift either blue or red. Using the above calculations, it should be possible to engineer structures that maximize the already large nonlinear effects.