Optical phonon damping in the ultrathin-layer GaAs/AlAs superlattices

We performed the precision measurements of the near-normal far-infrared reflection and transmission spectra of the MBE-grown (GaAs)(n)/(AlAs)(n) (n = 1, 2, 4) superlattices. The results obtained show a noticeable (almost twofold) increase in the AlAs-phonon damping when n is decreased from 4 to 1. We consider possible physical mechanisms of this increase and compare our results with those obtained by other authors. The main implication of the work is that the increase in the TO-phonon damping may be related to interface broadening whose role becomes more important when the superlattice period decreases. (C) 1999 Academic Press.