Quantum size effect in self-organized InAs/GaAs quantum dots

The quantum size effect of exciton transitions is investigated experimental ly and theoretically for self-organized InAs/GaAs quantum dots (QD's). Phot oluminescence excitation (PLE) experiments are reported for a series of sam ples with QD's varying in average size, revealing size-dependent excitation resonances. Temperature-dependent measurements show that the PLE spectra m irror the absorption spectra of QD's with a certain ground state transition energy. The observed PLE resonances are identified based on their energy, relative intensity, and sensitivity to size variations in comparison to res ults of eight-band k.p calculations for pyramidal InAs/GaAs QD's with {101} side facets. Band mixing, strain, and the particular geometry of the three -dimensional confinement lead to a rich fine structure with a variety of '' forbidden'' excitonic transitions. A good agreement between experiment and theory is found for large QD's (E(det)less than or similar to1.1 eV), where as the agreement becomes worse for smaller QD's. The discrepancies arise, m ost likely, from the uncertainties in the size- and growth-dependent variat ions of the QD shape and composition as well as Coulomb-induced localized w etting layer states.