Electron-acoustic phonon interaction in a single quantum dots layer: Acoustic mirror and cavity effects
We report on resonant Raman scattering in a single layer of self-assembled InAs/InP quantum dots (QDs). Oscillations are observed in the low frequency spectra. Experiments were performed on samples with different cap and oxide layers. By combining both experiments and Raman scattering simulations, we show that these oscillations are due to the interaction between the QD electronic states and standing acoustic waves. These standing acoustic waves are due to reflection at the sample surface which behaves as an acoustic mirror. The intensity oscillation period is shown to depend on the distance between the sample surface and the QD layer. A rather complex modulation of the surface induced intensity oscillations is observed. We show that this modulation is due to the oxide layer present at the sample surface. The oxide layer behaves as an additional acoustic cavity. We discuss how the electron-acoustic phonon interaction depends on the acoustic mirror and cavity effects. We also point out the likeness between the surface induced intensity oscillations and Raman scattering interferences.