EXCITONIC PROPERTIES OF ISOLATED NANOMETER-SIZED INAS ISLANDS IN A GAAS MATRIX

Isolated nanometer-sized LnAs islands formed in a GaAs matrix by direct epitaxial growth are studied by optical spectroscopy to get information about the energy relaxation processes of the photoexcited system. Two different relaxation mechanisms that depend upon excitation density are identified: At higher density photoluminescence excitation exhibits a strong oscillatory behavior due to separate carrier relaxation, whereas at lower density direct photogeneration of excitons is dominant. Both results ensue from the strong electron-LO-phonon interaction in the system. The study of these well-characterized samples with isolated InAs islands gives insight into the optical properties of quantum dot systems made of this materials system. (C) 1995 American Institute of Physics.