  We present studies on Coulomb interactions in single self-assembled CdTe
quantum dots. We use a field effect structure to tune the charge state of the
dot and investigate the impact of the charge state on carrier wave functions.
The analysis of the quantum confined Stark shifts of four excitonic complexes
allows us to conclude that the hole wave function is softer than electron wave
function, i. e. it is subject to stronger modifications upon changing of the
dot charge state. These conclusions are corroborated by time-resolved
photoluminescence studies of recombination lifetimes of different excitonic
complexes. We find that the lifetimes are notably shorter than expected for
strong confinement and result from a relatively shallow potential in the
valence band. This weak confinement facilitates strong hole wave function
redistributions. We analyze spectroscopic shifts of the observed excitonic
complexes and find the same sequence of transitions for all studied dots. We
conclude that the universality of spectroscopic shifts is due to the role of
Coulomb correlations stemming from strong configuration mixing in the valence
band.
