Resonant optical excitation and intermixing in InAs/AlAs single quantum dots

The optical excitation spectra of single self-organized InAs/AlAs quantum dots reveal transitions to excited states involving quantum dot phonons. Resonant excitation is observed at 31 and 41 meV, corresponding to the “InAs-like” and “AlAs-like” optical phonons of InAlAs with low Al concentration. Polarization-resolved measurements reveal separate resonances at the fine structure split exciton levels. The present results demonstrate that both LO phonons in a mixed quantum dot can contribute to the relaxation of excited states and represent a direct measurement of the intermixing in a single quantum dot.