Barrier height versus confinement efficiency for the optical phonons in GaAs/AlxGa1-xAs heterostructures

The applicability of the infinite-barrier scheme to the study of the confinement mechanism for the optical phonons in GaAs/AlxGa1-xAs heterostructures is critically addressed. In the framework of a bond-charge-model calculation, we demonstrate that the line shape of LO1 GaAs-like displacement patterns differs from a sinelike function and depends on the Al content of the ternary barrier, preventing the extension of the infinite-barrier scheme to ternary systems. Finally, the analysis of Raman intensities is indicated as a suitable probe of the confinement efficiency because of its sensitivity to the displacement pattern line shape. © 1994 The American Physical Society.