Electronic Structure and Electrical Conductivity of Ge2Sb2Te5 Heterostructures With Varying Stacking Configurations

Abstract

Phase change materials (PCMs) are an important group of materials with distinct solid phases. In this group, Ge2Sb2Te5 (GST) is a promising compound with many technological applications. GST can be grown into a heterostructure where the phase change is spatially confined, resulting in improved efficiency. In the present work, the electronic properties and electrical conductivity of GST heterostructures with various stacking configurations are studied using density functional calculations. Geometry optimization calculations show the importance of the van der Waals (vdW) correction that results in a decrease of the out-of-plane lattice parameter. Band structure calculations show metallic or semimetallic character for some configurations, whereas the others are semiconductors with bandgaps below 1 eV near the Γ point. The in-plane electrical conductivity is higher than the out-of-plane one, with differences between the configurations at most three- to fourfold, indicating they all belong to the same phase. The Te atoms are negatively charged, while the Ge and Sb atoms have positive charges. There is no significant charge transfer between the blocks separated by vdW gaps although visible electron accumulation occurs within the gaps. The observed stacking-dependent changes can possibly be applied to the design of interfacial PCMs with new properties and functionalities.