Tunneling effects in Cd_0.24Zn_0.76Te/ZnTe asymmetric double quantum wells

Photoluminescence (PL) measurements have been performed to investigate the tunneling effects in Cd_0.24Zn_0.76Te/ZnTe asymmetric double quantum wells (DQWs). The Cd_0.24Zn_0.76Te/ZnTe DQWs were separated by a ZnTe step potential barrier width between 30 and 200 Å. The results for the PL data at 20 K showed clearly that the excitonic transition behavior from coupling to uncoupling depended on the embedded ZnTe barrier thickness. The electronic subband energies and the wavefunctions in the quantum wells were calculated by an envelope-function approximation which took into account the strain effects, and the calculated interband transition values were in reasonable agreement with those obtained from the PL measurements. The coupling behavior between the two Cd_0.24Zn_0.76Te wells which were separated by a ZnTe barrier in the asymmetric DQWs was investigated theoretically, and the calculated results were in qualitative agreement with those determined from the experimental data. These results indicate that Cd_0.24Zn_0.76Te/ZnTe asymmetric coupled DQWs hold promise for potential applications such as new types of optical bistability switching devices in the blue-green region of the spectrum.