Phonons and radiative recombination in self-assembled quantum dots

The radiative recombination of photocarriers has been studied in various self-assembled ${\mathrm{In}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs and ${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{In}}_{1\mathrm{-}\mathit{x}}$As/${\mathrm{Al}}_{\mathit{y}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{y}}$As quantum dot samples, prepared with the spontaneous island formation during molecular-beam epitaxy. Depending on the relative values of the interlevel spacings and the phonon energies, some structures display strong enhancement of the photoluminescence for excitation energies permitting resonant phonon relaxations, or strong level filling and emission from the excited states with saturation of the ground states at higher excitation intensities.