Strain induced quantum dots (QDs) have attracted more and more attention in recent years due to its potential applications in optoelectronic devices such as light-emitting devices and lasing diodes. Practical devices based on QDs are expected to exhibit high differential gain

low threshold current

and high characteristic temperature comparing with those based on thin films

two-dimensional quantum well and one-dimensional quantum wire structures. To realize these priorities

the study on growth and optical properties of QDs is necessary. Up to now

the study on QDs mainly focuses on Ⅲ Ⅴ systems

In(Ga)As/GaAs system

for example. As for Ⅱ-Ⅵ systems

CdSe/ZnSe attracts most attention. However

The CdSe/ZnSe system

which has relative narrow band gap

can only cover the spectrum range from red to green region. As is known

Zn

x

Cd

1-

x

Se can extend its spectrum to the whole visible range by varying

x

value. Therefore

the study on the optical properties of ZnCdSe QDs is not only important but also necessary. Additionally

the realization of long lifetime light-emitting devices based on ZnCdSe quantum well structures makes the study more attractive. In the present paper

ZnCdSe QDs have been fabricated under Stranski Krastanow (S-K) mode on GaAs substrate. Atomic force microscopy investigation confirmed the formation of the dots. The excitonic properties of the QDs were investigated by photoluminescence (PL) measurements. The appearance of a kind point in the temperature-dependent PL intensity at about 20K verifies the observation of AFM. With increasing the interruption time between the dot formation and capping

the PL spectra of the QD structures show obvious broadening in full width at half maximum and redshift of peak energy

and the ionization energy

which is induced from the temperature dependence of integrated intensity

decreases significantly with increasing the interruption time. These facts can be attributed to the variations in dot size induced by the ripening process occurring in the growth interruption

in which

the larger dots become bigger at the cost of the smaller ones. Therefore

the PL spectrum broadens because of the increased nonuniformity of the size distribution of the dots. Meanwhile

the peak energy shifts to low energy side

and the ionization energy decreases

resulted from the increase of the dot size. 