Phonon freedom and confinement in GaAsAlxGa1−xAs superlattices

✍ Scribed by C. Colvard; R. Fischer; T.A. Gant; M.V. Klein; R. Merlin; H. Morkoc; A.C. Gossard

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 394 KB
• Volume: 1
• Category: Article
• ISSN: 0749-6036
• DOI: 10.1016/0749-6036(85)90033-3

✦ Synopsis

Phonon modes in GaAs-AIxGaI_xAS superlattices simplify when the phonon wavevector q is perpendicular to the plane of the layers. We have studied such modes using a Raman back-scattering technique on SL's grown by MBE. The results are consistent with simple ideas of LA phonon freedom and hO phonon confinement suggested by one-dimensional lattice dynamical calculations.

The longitudinal acoustic (LA) modes show zone folding due to mini-zone formation.

Their frequencies occur in doublets linearly dependent on q and show little mini-gap formation. This is consistent with a picture of approximately free plane wave propagating through the interfaces with Raman coupling due to SL layering of the photoelastic coefficient.

By contrast, Raman data on LO modes in small period GaAs-AIAs SL's suggest that these modes are standing waves strongly confined in either GaAs or AIAs.