EFFECTS OF INTERFACIAL ASYMMETRY ON THE FOLDED LONGITUDINAL ACOUSTIC PHONONS IN SI GE AND GAAS/ALXGA1-XAS SUPERLATTICES/

A theoretical analysis is performed of the effects of interfacial asym metry in Si/Ge and GaAs/AlxGa1-xAs superlattices. It is assumed that t he interfacial alloy density of both superlattices changes linearly. I t is shown that the longitudinal acoustic (LA) phonon energies decreas e (increase) if the interfaces resulting from the growth of Ge on Si o r AlxGa1-xAs on GaAs are thicker (thinner) than the interfaces resulti ng from the growth of Si on Ge or GaAs on AlxGa1-xAs. These effects in crease with the degree of interfacial asymmetry, and are stronger in S i/Ge than in GaAs/AlxGa1-xAs superlattices.