Electronic subband studies on CdxZn1-xTe/ZnTe symmetric coupled double step quantum wells

Structural and optical properties on new kinds of the CdxZn1-xTe/ZnTe coupled double step quantum wells have been studied by transmission electron microscopy (TEM) and photoluminescence (PL) measurements. The results of the TEM measurements on the symmetric coupled double step quantum wells show that two kinds of a 50-Angstrom Cd0.08Zn0.92Te shallow step well and a 50-Angstrom Cd0.26Zn0.74Te deep step well bounded by two ZnTe barriers are separated by a 30-Angstrom ZnTe potential barrier. A PL spectrum measured at 15 K show the dominant excitonic transitions from the ground state electronic subband to the first heavy-hole band together with transitions from the first excited electronic subband to the second heavy-hole band. The electronic subband energies and energy wavefunctions in the CdxZn1-xTe quantum wells are calculated by a transfer matrix method which takes into account the strain effects. The calculated interband transition values are in reasonable agreement with those obtained from the PL measurements. These results can help improve understanding of the electronic properties of the unique CdxZn1-xTe/ZnTe coupled double step quantum wells for the application of new types of optical modulators and detectors in the blue-green region of the spectrum utilizing the advantages of the coupled double step quantum wells. (C) 1998 Elsevier Science Ltd. All rights reserved.