Ellipsometric study of sinusoidally modulated ZnSeTe superlattices

We report an optical study of sinusoidally modulated ZnSeTe superlattices using spectroscopic ellipsometry. The pseudodielectric function 〈∈〉 = 〈∈₁〉 + i〈∈₂〉 was determined for the photon energy range 1.5-6.5 eV and critical point parameters were obtained by fitting model line shapes to numerically calculated second energy derivatives of 〈∈〉. As the degree of the compositional modulation of the superlattice increased, the energies of E₁-R₁ and E¹ + Δ₁ - R₁ either decreased or increased depending on the superlattice period. We explain this behavior in terms of an interlayer coupling and quantum-confinement effect characteristic, respectively, for the two geometries.