The electronic structures of the (CdTe)Nw1 (ZnTe)Nb (CdTe)Nw2-ZnTe(001) symmetric and asymmetric double-quantum wells (s-DQW and a-DQW) are presented. The tight-binding sp3s* method, with inclusion of spin-orbit coupling, is used to calculate the band-gap energy, quantum-confinement energy, carrier planar-spin-averaged wavefunction-squared amplitudes and band structures versus the barrier thickness (Nb), well widths (Nw1 and Nw2) and valence-band offset (VBO). Special attention was given to the well-to-well coupling behaviors in both a-DQW and s-DQW and the estimation of the critical barrier thickness Lcritb corresponding to their decoupling. In the case of a-DQW, the wavefunctions of bound states are found to have strong tendency to localize in one of the two wells and, as a consequence, the decoupling occurs at Lcritb ≃ 18 Å, much shorter than the case of s-DQW (where Lcritb ≃ 38 Å). Our results of Eg are in excellent agreement with the available photoluminescence data and the structural and optical qualities of the experimental samples are discussed.
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