Selective excitation through multiphonon emission of ZnCdTe quantum dots embedded in Zn-rich ZnCdTe quantum wells

We study the energy relaxation of electron-hole pairs in ZnCdTe quantum wells, which is followed by a trapping in self-organized CdTe/ZnTe islands. An optical-phonon emission cascade is observed, giving rise to a selective population of the Cd-rich islands. Using photoluminescence excitation spectroscopy, we determine the energy of the phonons involved in the process. We study also the evolution of the quantum efficiency of the phonon emission process as a function of the photon energy, the number of emitted phonons, and temperature. Moreover, we evidence coupled exciton-phonon states in the quantum dots which explain the trapping of the electron-hole pairs and their recombination.