(CdZnTe,ZnS)/ZnTe复合量子阱的光学特性研究

Optical Properties of (CdZnTe, ZnS) / ZnTe Composite Quantum Wells Structure

设计并制备了一种新型的（ＣｄＺｎＴｅ，ＺｎＳ）／ＺｎＴｅ复合量子阱结构。使ＣｄＺｎＴｅ 量子阱中的激子有可能在短时间内隧穿到ＺｎＳ 阱层，从而达到提高光双稳器件“关”速度的目的。并通过对发光特性的研究证实在我们设计的结构中横向激子隧穿的存在，从而为进一步研究超高速光开关提供了实验依据。

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 (H2S) were used as precursors. The system pressure of chamber was kept at 4.0×104Pa 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.