Probing the intermixing in In(Ga)As/GaAs self-assembled quantum dots by Raman scattering

We show that Raman scattering is a sensitive technique for probing the degree of Ga intermixing in In(Ga)As/GaAs self-assembled quantum dots (QDs). The shifts of the QD phonon frequency that we observe are explained by the modification of the strain due to Ga incorporation into the QDs from the GaAs matrix during growth. Using an elastic continuum model, we estimate the average In content of the dots from the QD phonon frequency. The varying amount of intermixing in QDs grown with different In compositions, QD layer thicknesses, growth temperatures, and stacking spacer layer thicknesses are investigated. The Raman data indicate that Ga intermixing is larger for QD samples with low In(Ga)As coverage thickness and/or high growth temperature and, in multilayered systems, for samples with small GaAs spacer layers.