The ZnCdSe/ZnSe asymmetric double quantum wells(ADQW)samples studied were grown on(100)Si-doped GaAs substrates by low pressure(LP)MOCVD. The sample structure consists of a 1μm ZnSe buffer layer followed by ten periodes of Zn

0.72

Cd

0.28

Se/ZnSe ADQW and then a 60nm ZnSe cap layer. Each period of ZnCdSe/ZnSe ADQW includes one narrow ZnCdSe quantum well

one thin ZnSe barrier and one wide ZnCdSe quantum well. Each period of the ADQW was separated by a 40nm ZnSe barrier. Exciton tunneling has been studied in the ZnCdSe/ZnSe ADQW. There are two emission peaks of the time-resolved spectra of the ADQW corresponding to

n

=1 heavy hole recombination from the wide well (WW) and narrow well (NW)

respectively. It is obvious that the

n

=1 heavy hole excitonic emission from the WW dominates the spectra

and the

n

=1 heavy hole excitonic emission from the NW decreases and disappears gradually with increasing the delay time. Considering the exciton tunneling in the ADQW

this phenomenon can be explained. Under stronger excitation

the tunneling of free electron and free hole are also observed in the ADQW. Due to different tunneling time of free electron and free hole

space charge effect was observed in the ADQW

which leaded to the foundation of the internal electric field. The excitation intensity dependence of the luminescence intensity in the WW and NW as shown in fig.5 can be explained by foundation of the internal electric field. The spontaneous and stimulated emission have been studied in the ZnCdSe/ZnSe ADQW. For spontaneous emission of the ADQW

the exciton recombination both in the NW and WW is influenced by two factors

the exciton tunneling and the thermal dissociation processes. For the NW

the two factors have the same influence on the emission intensity

but for the WW

the influence on the emission intensity of two factors are contrary. The change of the emission intensity in the WW is determined by the stronger one. For stimulated emission of the ADQW

owing to the difference of the energy levels between the WW and the NW

the carriers tunnel from the NW to the WW

which can influence the emission effectively.The carrier tunneling is conductive to lasing from the WW.