Electronic structure, effective masses and optical properties of perfect and imperfect HgTe-Hg1-xCdxTe and HgTe-Zn1-yCdyTe superlattices

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Abstract
The authors have carried out pseudopotential calculations of the electronic structure, effective masses and optical spectra of HgTe-Hg1-xCdxTe and HgTe-Zn1-yCdyTe (strained) superlattices. In the calculations, the microscopic crystal potential and relativistic corrections are fully accounted for. The main purpose of the study is to investigate the relationship between the localisation of electron states near the interface and the effects of the microscopic crystal potential and strain zone folding. The authors show that while most average quantities associated with the effect of confinement such as the position of the minibands along the superlattice axis can be well accounted for by the effective mass approximation, the localised phenomena at the interface reflect the large difference of the atomic relativistic potentials of Cd (Zn) and Hg. In particular they show that in Cd compounds (i) the heavy hole mass is m*HH/mo=0.013 in a 100.3 AA HgTe and 38.8 AA CdTe superlattice, compared with 0.017 from experiment, and (ii) m*HH rapidly increases with increasing x for given layer widths, in favourable agreement with experimental evidence.

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