Temperature dependence of Raman scattering by acoustic phonons in a superlattice GaAs/AlGaAs in strong magnetic fields

We observed simultaneously two types of Raman spectra in a GaAs/AlGaAs superlattice under high magnetic field: a folded longitudinal acoustic phonon, IFA, and a structureless background, IB. The temperature dependence of the intensities in both spectra was studied in the range 2–100K and it was established that the background spectrum is due to the first-order Raman scattering from acoustic phonons with a wide range of wave vectors. We obtained the expression for the intensities ratio IB/IFA. It depends on the relationship between the homogeneous and the inhomogeneous broadening of the intermediate state of the photoexcited e-h pair. A rapid decrease of IB observed at T 30K is thought to be due to the increase of the homogeneous width with temperature.