Light and heavy excitons in strained CdTe/CdZnTe quantum wells

The spectra of photoluminescence and polarized reflection under normal and oblique incidence of light from structures with quantum wells with symmetric Cd$_{0.9}$Zn$_{0.1}$Te/CdTe/Cd$_{0.9}$Zn$_{0.1}$Te and asymmetric Cd$_{0.9}$Zn$_{0.1}$Te/CdTe/Cd$_{0.4}$Mg$_{0.6}$Te barriers have been studied. Due to the mechanical stresses caused by the mismatch of the crystal lattices of the wells and barriers, the energy of light holes in quantum wells was higher than in barriers, i.e., the band structure for them was of type II. However, in the reflection spectra, the lines of heavy and light excitons had comparable intensities. In structures with symmetric barriers, exciton resonances, which do not appear in the photoluminescence spectra, were found in the reflection spectra. A detailed calculation of the energy levels and reflection spectra has been carried out.