The optical bistability device

as a basic device for optical computer

its most attractive property will be the ultrahigh rate of opening and closing.The ultrahigh rate of opening can be realized by now.However

limited by the life of carriers in semiconductor

the ultrahigh rate of closing is difficult to realize.In this paper

a new type of(CdZnTe

ZnS)/ZnTe composite quantum wells structure was devised for im-proving the rate of closing in the optical bistability device.In this structure

the ZnS and ZnTe form Ⅱ-type superlattices structure

and the band gap of ZnS is wider than that of CdZnTe.Then

the introduction of ZnS well layer will have no effect on the nonlinear property of ZnTe/CdZnTe.The exciton in the CdZnTe well layer will cross through the ZnTe barrier layer into the ZnS well layer in a very short time.Then

the tunnelling can reduce the life of exciton and realize the high closing rate of the optical bistability device.Samples were fabricated by low-pressure metalorganic chemical vapor deposition(LP-MOCVD) on GaAs(100) substrates.Diethyl-telluride(DETe)

dimethyl-cadmium(DMCd)

dimethyl-zinc(DMZn) and sulfureted hydrogen(H

2

S) were used as precursors.The system pressure of chamber was kept at 4.0×10

4

Pa and the temperature was at 420℃.Samples consisted of a ZnTe buffer layer

40 periods of composite quantum well structure(CdZnTe well layer-ZnTe barrier layer-ZnS well layer-ZnTe barrier layer) and a ZnTe capping layer.Different sample had different thickness of ZnTe barrier layer.Through studying PL spectra of the samples

the luminescence of cross exciton was obtained.The tunnelling of cross exciton was verified by analysing the PL intensity rate of carriers provider well and carriers receiver well.Furthermore

the multilevel Raman peak can also verify the existence of tunnelling during the process of lu minescence.Those conclusions indicated the validity of this composite quantum wells device for reducing the life of exciton in the CdZnTe well and provided the evidence in experiment for further research of ultrahigh rate optical switch device.