Quantum-dot phonons in self-assembled InAs/GaAs quantum dots: Dependence on the coverage thickness

We study the phonons of self-assembled InAs/GaAs quantum dots for different coverage thicknesses L. The additional Raman feature detected between the GaAs transverse optical and the InAs longitudinal optical modes, which we assign to phonons of the dots, exhibits an upward frequency shift with L. This shift is attributed to compressive strain in the dots and, on the basis of its dependence on L, we show that these phonons arise from the quantum dots and not from the wetting layer.