The CdSe/ZnSe asymmetric quantum wells sample were grown on GaAs substrates by MOCVD.The samples consist of a 112 nm ZnSe buffer layer followed by two 22ML and a 10MLs CdSe quantum wells and then a 51 nm ZnSe cap layer.The ZnSe barriers between the quantum wells are 34 nm and 3.9 nm

respectively.Asingle quantum wells was also prepared as a comparison with the asymmetric quantum wells.It contains three 10ML CdSe quantum wells separated by a 34 nm ZnSe barrier and it was fabricated at the same condition with the asymmetric quantum wells.Spontaneous emission has been studied in the CdSe/ZnSe asymmetric quantum wells.There are two emission peaks of the photoluminescence spectra of the sample corresponding to n=1 heavy hole exciton recombination from the wide well (WW) and narrow well (NW) in the temperature range of 82 to 141 K

respectively.The emission peak of the NW can not be seen after 141 Kand is identified by the spontaneous emission spectrum of the single quantum wells at 82 K.The exciton recombination both in the NW and WW is influenced by two factors:the exciton tunneling and the thermal dissociation processes.For the WW

the influences on the emission intensity of two factors are contrary.The change of the emission intensity in the WW is determined by the stronger one:the exciton tunneling plays the more important role in the temperature ranging from 82 Kto 141 Kand the thermal dissociation processes play the more important role for the rest of the temperature.For stimulated emission of the CdSe/ZnSe asymmetric quantum wells

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.Space charges caused by different tunneling rate between electrons and holes lead to the formation of the internal electric field which affects carriers tunneling.As the result of the internal electric field effect

the changing of the electrons density excited with excitation intensity is super-linear.The carrier which decides the changing of the peak energy in the wide well is exciton which comes from two sources

one is excited by photon in the wide well

and the other one is that tunneling from the narrow well.