THEORY OF PHONON REPLICAS IN SUPERLATTICE PHOTOLUMINESCENCE EXCITATION-SPECTRA

We have calculated photoluminescence excitation spectra for LO-phonon- assisted hot carrier recombination in short period GaAs/AlxGa1-xAs sup erlattices. The line shape is different than that for a quantum well, due to the effect of the superlattice miniband. This allows a range of transitions at different energies,as opposed to a unique transition i n the quantum well case. The width of the feature is comparable to tha t observed experimentally. To calculate the luminescence intensity we evaluate the density of states, the oscillator strength, and the elect ron-LO-phonon scattering rate. We account for the valence-band nonpara bolicity by solving the Luttinger Hamiltonian. We find that the domina nt factor is the density of states, and that it is therefore essential to include the valence-band nonparabolicity.