Phase change alloys are used for non-volatile random access memories exploiting the conductivity contrast between amorphous and metastable, crystalline phase. However, this contrast has never been directly related to the electronic band structure. Here, we employ photoelectron spectroscopy to map the relevant bands for metastable, epitaxial GeSbTe films. The constant energy surfaces of the valence band close to the Fermi level are hexagonal tubes with little dispersion perpendicular to the (111) surface. The electron density responsible for transport belongs to the tails of this bulk valence band, which is broadened by disorder, i.e., the Fermi level is 100 meV above the valence band maximum. This result is consistent with transport data of such films in terms of charge carrier density and scattering time. In addition, we find a state in the bulk band gap with linear dispersion, which might be of topological origin.
@article{arxiv.1708.08787,
title = {Mapping the band structure of GeSbTe phase change alloys around the Fermi level},
author = {Jens Kellner and Gustav Bihlmayer and Marcus Liebmann and Sebastian Otto and Christian Pauly and Jos Emiel Boschker and Valeria Bragaglia and Stefano Cecchi and Rui Ning Wang and Volker L. Deringer and Philipp Küppers and Priyamvada Bhaskar and Evangelos Golias and Jaime Sánchez-Barriga and Richard Dronskowski and Thomas Fauster and Oliver Rader and Raffaella Calarco and Markus Morgenstern},
journal= {arXiv preprint arXiv:1708.08787},
year = {2018}
}