The extraordinary electronic and optical properties of the crystal-to-amorphous transition in phase-change materials 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/Sb2Te3 chalcogenide superlattice films. We determine, for films with varying stacking sequence and growth methods, the density and scattering time of the free electrons, and the characteristics of the valence-to-conduction transition. It is found that the free electron density decreases with increasing GeTe content, for sub-layer thickness below ∼3 nm. A simple band model analysis suggests that GeTe and Sb2Te3 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 properly choosing the deposition layer thickness and we derive a model for arbitrary film stacks.
@article{arxiv.1605.08871,
title = {Interband characterization and electronic transport control of nanoscaled GeTe/Sb$_2$Te$_3$ superlattices},
author = {Antonio Caretta and Barbara Casarin and Paola Di Pietro and Andrea Perucchi and Stefano Lupi and Valeria Bragaglia and Raffaella Calarco and Felix Rolf Lutz Lange and Matthias Wuttig and Fulvio Parmigiani and Marco Malvestuto},
journal= {arXiv preprint arXiv:1605.08871},
year = {2016}
}