Employing two different growth methods: standard molecular beam epitaxy (MB
E) and low-temperature atomic layer epitaxy (ALE) with subsequent annealing
, we have obtained high-quality quantum dot structures consisting of CdSe e
mbedded in ZnSe. Single dot emission lines are observed in micro-luminescen
ce. The samples have been investigated by further optical methods including
time-resolved photoluminescence under resonant excitation at 4.2 K. Distin
ct properties of systems with three-dimensional confinement are observed su
ch as the suppression of the interaction between isolated quantum dots (QDs
). In standard quantum wells tunneling/hopping processes generally lead to
a pronounced red shift of the luminescence over time due to a lateral local
ization of excitons in potential fluctuations. A much less pronounced red s
hift is observed for the QDs reflecting only the different lifetimes of sin
gle dots and higher excited states. The red shift completely vanishes under
resonant excitation that selectively excites only a few QDs of the ensembl
e in the layer. Typical behaviour is also observed from the halfwidth of th
e quantum dot emission. (C) 1999 Academic Press.