Oscillatory behavior in the photoluminescence excitation and photoconductivity spectra of GaAs-AlAs superlattices

Oscillations due to the emission of confined LO GaAs phonons by photoexcited electrons have been observed in the ({~}4 K) excitation spectra of both the photoluminescence and photoconductivity of GaAs-AlAs superlattices. The period of the oscillations, which is increased over that observed in bulk GaAs, allows us to determine the in-plane heavy-hole mass which gets progressively heavier as the AlAs thickness is reduced. For one sample, a 60-period 25-A{}--8-A{} GaAs-AlAs superlattice, we estimate the heavy-hole exciton binding energy to be {~}8.5 meV. Measurements on the pseudodirect 23-A{}--19-A{} GaAs-AlAs sample indicate that the electron-phonon interaction in the GaAs initially dominates over transfer into the AlAs X valleys.