Study of phonons in self-assembled InAs quantum dots embedded in an InGaAlAs matrix

We studied phonon modes propagating along the [3 1 1] direction in highly ordered, stacked InAs QDs embedded in an InGaAlAs matrix grown on InP(3 1 1) substrate by Raman spectroscopy. The Raman spectra showed clear doublets of folded quasi-longitudinal modes which have mixed transverse and longitudinal character. A broad feature observed in the Raman spectra was attributed to superposition of densely folded and/or confined phonon modes that is with agreement with our previous theoretical calculation. The phonon gap was observed and compared with our theoretical calculations.