Abstract
Heterostructures with atomically thin double quantum wells based on CdTe/ZnTe are investigated by optical spectroscopy (photoluminescence and reflectivity methods) as a function of temperature and density of excitation. Heavy and light exciton luminescence lines are observed with comparable intensities and different temperature behaviors (they cross each other at about 65° K). All these features agree with a complete calculation that takes into account both a very small chemical band offset for such monolayer CdTe inclusions in the ZnTe matrix (namely, 2%), and, consequently, the importance of Coulombic interaction in these double quantum wells.
Highlights
Semiconductor compounds A2B6, in particular CdTe and ZnTe, are often used for basic research as a model object
All these features agree with a complete calculation that takes into account both a very small chemical band offset for such monolayer CdTe inclusions in the ZnTe matrix, and, the importance of Coulombic interaction in these double quantum wells
The heavy and light excitons lines are identified. These lines have different temperature dependences, clearly indicating that the heavy exciton is mainly located in the CdTe layers and the light one is in the ZnTe layers
Summary
Semiconductor compounds A2B6, in particular CdTe and ZnTe, are often used for basic research as a model object. The spectrum normalized to the maximum shows that the intensities of the doublet lines are equal in the polarization perpendicular to the well plane (Fig. 4) This partially confirms our interpretation of the short-wave line as a line of a heavy exciton and the long-wave one as a line of a light exciton. The calculation showed that the energy position of the light exciton level is practically independent of the bandgap and is “tied” to the valence band of ZnTe. At the same time, the energy position of the heavy exciton level linearly depends on the band offset and is “tied” to the CdTe band. Knowing the magnitude of the total and deformation band offsets, we can determine the chemical band offset in the valence band in a CdTe/ZnTe system, the strength of the potential, and the size of the wave function. The chemical band offsets in the valence band turned out to be ∼10 meV, which is equal to 2% of the total chemical band offset
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