A MODEL FOR LONGITUDINAL OPTICAL PHONONS AND ELECTRON-PHONON COUPLING IN GAAS/GAALAS MULTILAYER STRUCTURE

A new model for long-wavelength longitudinal optical phonons in GaAsGaAlAs multi-layer structures is presented. Depending on the layer, the relative ionic displacements are written on the basis of GaAs or GaAs-type longitudinal optical phonons and treated in the framework of the Born-Huang model generalized to include isotropic dispersion effects in the Brillouin zone centre. For double heterostructures, a finite number of quantized confined modes is found. Interplay between the long range Coulomb interaction, which couples the vibrations of adjacent GaAs layers, and confinement effects, which prevent the displacements of adjacent GaAs layers to overlap, is evidenced in the case of superlattices. The strength of the electron-phonon coupling in double heterostructures stays within a factor of 2 of the electron-bulk phonon effective coupling strength for practical values of the parameters. © 1990.