Over past twenty years our research work is concentrated at photoelectronics and luminescence in wide band gap Ⅱ-Ⅵ compound semiconductors and its low dimentional structure. The main research results can be concluded as follows:The first

free exciton emission under excitation of electric field was systematically studied. Free exciton emission and its longitudinal optical (LO) phonon replicas in ZnSe and CdS MIS diodes have been identified in terms of Gross's theory. Pure green

blue

blue-violet and violet electroluminescence(EL) at room temperature(RT) have been obtained in Ⅱ-Ⅵ compound MIS diodes

respectively. The origin of two blue EL bands at RT in ZnSe MIS diodes is attributed to emission related to free exciton. The homogeneity of blue EL in ZnSe MIS diodes has been improved by using a suitable insulating layer. The second

optical bistatility (OB) in ZnSe-based multiple quantum wells (MQWs)was studied. ZnSe-based MQWs with high quality were fabricated by LP/AP MOCVD and identified by XRD

PL and SEM measurements. The OB with ns response was observed in ZnSe-ZnS MQWs at 77K for the first time. The origin of the OB is attributed to the dispersive nonlinearity due to the effect of excitonic saturating absorption. The OB with ps response was observed in ZnTe-ZnSe MQWs and ZnTe-ZnS MQWs at RT for the first time. The mechanism of the OB is attributed to increasing absorption effects due to the band gap shrinkage of the MQWs in high density photo-excitation. The OB in ZnSe-ZnS MQWs optical waveguide is also observed at RT for the first time

the switching response time of the OB is about 500ps and the threshold switching power is 1μW

which is much lower than that reported before. The third

the spontaneous and stimulated emission in ZnSe-based MQWs was studied. For Zn

0.8

Cd

0.2

Se-ZnSe MQWs four bands from PL spectrum were observed at 17K

and can be attributed to the

n

=1

2hh and 1h exciton transition

respectively. The stimulated emission from the cleaved edge of the sample with different cavity length were observed at 77K. It is noticed that the sample with shorter Fabry-Perot cavity length has the larger threshold excitation and more mode spacing. For ZnSe-ZnS MQWs the stimulated emission is observed and attributed to the exciton-exciton interactions. The elastic properties and related effects of the elastic strain from ZnSe-ZnSeS strained layer superlattice (SLS) have been studied by means of Brillouin spectroscopy. The longitudinal optical phonon modes LO

m

both in ZnSe well and ZnS barrier on ZnSe-ZnS SLS are observed by means of Raman scattering spectra. The fourth

the ZnCdSe-ZnSe ADQWs samples studied were grown on GaAs(100) substrate by LP-MOCVD at 350℃. The spontaneous emission in the sample has been studied. The exciton emission both in the narrow well(NW) and in the wide well(WW) is influenced by two factors:the exciton tunneling and thermal dissociation processes. For the NW the two factors have the same influence on emission intensity

but for the WW the influence are contrary. The change of the emission intensity in the WW is determined by the stronger one. The stimulated emission in the sample has also been studied. The carrier tunneling through the thin barrier is conductive to the stimulated emission from the WW

and the threshold can be lowered by optimizing the structure. The fifth

CdSe self-assembled quantum dots (SAQDs) were grown under S-K mode by LP-MOCVD. The formationprocesses of CdS SAQDs below the critical thickness was observed by atomic force microscopy (AFM) for the first time. It revealed that the formation mechanism of CdSe SAQDs under critical thickness was due to the effect of surface diffusion and strain release. Our results make it possible to observe the process of release strain directly. ZnSe

1-x

S

x

QDs were also grown under V-W mode by LP-MOCVD. The formation process of the QDs was studied by the surface morphologies and PL measurements. The sixth

growth and ultraviolet(UV) emission of ZnO thin film. ZnO thin films on Si substrate were fabricated by PECVD and thermal oxi