The extraordinary electronic and optical properties of the crystal-to-amorphous transition in phase-change materials have led to important developments in memory applications. A promising outlook is offered by nanoscaling such phase-change structures. Following this research line, we study the interband optical transmission spectra of nanoscaled GeTe/Sb 2 Te 3 chalcogenide superlattice films. We determine, for films with varying stacking sequence and growth methods, the density and scattering time of the free carriers, and the characteristics of the valence-to-conduction transition. It is found that the free carrier density decreases with increasing GeTe content, for sublayer thicknesses below∼ 3 nm. A simple band model analysis suggests that GeTe and Sb 2 Te 3 layers mix, forming a standard GeSbTe alloy buffer layer. We show that it is possible to control the electronic transport properties of the films by …