Structural property and interband transition studies on CdxZn1-xTe/ZnTe coupled step and rectangular quantum wells

Abstract

Transmission electron microscopy (TEM) and photoluminescence (PL) measurements have been performed to investigate the structural properties and the excitonic transitions on CdxZn1-xTe/ZnTe coupled step and rectangular quantum wells grown by double-well temperature-gradient vapor-transport deposition. High-resolution TEM measurements on the coupled step and rectangular quantum wells show that a 50 Angstrom Cd0.08Zn0.92Te shallow and a 50 Angstrom Cd0.26Zn0.74Te deep step well and a 100 Angstrom Cd0.08Zn0.92Te rectangular quantum well bounded by two ZnTe barriers are separated by a 30 Angstrom ZnTe embedded potential barrier. A PL spectrum measured at 15 K shows the dominant excitonic transition from the ground state electronic subband to the ground state heavy-hole subband (E-1-HH1). The excitonic transition energy corresponding to the (E-1-HH1) in the coupled step and rectangular quantum wells is affected by the existence of the 100 Angstrom Cd0.08Zn0.92Te rectangular quantum well. The electronic subband energies and energy wave functions in the CdxZn1-xTe asymmetric coupled 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 structure of the complicated CdxZn1-xTe/ZnTe coupled step and rectangular quantum wells. Furthermore, these CdxZn1-xTe/ZnTe asymmetric coupled quantum wells might hold promise for the new kinds of optoelectronic devices in the blue-green region of the spectrum. (C) 1999 Elsevier Science B.V. All rights reserved.