RAMAN-SCATTERING IN LONG-PERIOD SUPERLATTICES OF GAAS, ALAS, AND GA0.5AL0.5AS LAYERS

The behavior of phonons in long-period superlattices has been examined by use of Raman spectroscopy. The superlattices are composed of alternating layers of GaAs and AlAs with Ga0.5Al0.5As layers inserted periodically, their periods ranging from 102 to 103. Zone-folded modes which reflect long periods are observed in the spectra. Raman-intensity profiles of the zone-folded modes are calculated by use of an elastic continuum model and the bond polarizability concept. The umklapp process is also taken into account in the calculation of longer-period superlattices. Good agreement is obtained between the calculated and observed intensity profiles. It is shown that Raman-intensity analysis has the potential to provide information about the period, structure, and the coherence length of phonons within the superlattices. © 1990 The American Physical Society.