  We show that two major carrier excitation mechanisms are present in II-VI
self-assembled quantum dots. The first one is related to direct excited state -
ground state transition. It manifests itself by the presence of sharp and
intense lines in the excitation spectrum measured from single quantum dots.
Apart from these lines, we also observe up to four much broader excitation
lines. The energy spacing between these lines indicates that they are
associated with absorption related to longitudinal optical phonons. By
analyzing resonantly excited photoluminescence spectra, we are able to separate
the contributions from these two mechanisms. In the case of CdTe dots, the
excited state - ground state relaxation is important for all dots in ensemble,
while phonon - assisted processes are dominant for the dots with smaller
lateral size.
