PHONON COUPLING IN GAAS ALXGA1-XAS OBSERVED BY PICOSECOND RAMAN-SCATTERING/

We measure the hot phonon population of the GaAs LO phonons using a pi cosecond Raman scattering technique. Our samples were a series of GaAs /Al0.4Ga0.6As superlattices (SLS) with a fixed well width (L(Z)) and v arying barrier width (L(b)). An abrupt increase in the phonon generati on rate was observed as L(b) decreased over a narrow range. This is in terpreted as the onset of significant well-to-well coupling of the con fined GaAs LO phonons. An estimate of the LO phonon penetration depth into the Al0.4Ga0.6As barriers is obtained from this transition.