Transition behaviors from coupled-to-uncoupled CdTe-ZnTe symmetric versus asymmetric double quantum wells

The coupling behaviors between symmetric versus asymmetric CdTe-ZnTe double quantum wells (DQWs) are theoretically investigated based on the application of the sp3s* tight-binding method including the spin-orbit interaction. This method is used to calculate the band structures of the (CdTe)Nw1(ZnTe)Nb(CdTe)Nw2-ZnTe DQWs versus the barrier thickness (Nb), and well widths (Nw1 and Nw2). Special attention was given to the decoupling behaviors between the wells in both symmetric and asymmetric cases. The decoupling of the asymmetric DQWs is found to occur at a critical barrier thickness (of about Lbcrit≃18A˚) shorter than the case of symmetric DQWs (of about Lbcrit≃38A˚) because, in the former case, the bound state wavefunctions have more tendency to localize in one of the two wells. Our modelling of asymmetric DQWs (with Nw1=6 and Nw2=3) yields results in excellent agreement with the available experimental photoluminescence data.