Disorder-Induced Localization in Crystalline Pseudo-Binary GeTe-Sb2Te3 Alloys between Ge3Sb2Te6 and GeTe

Abstract

Disorder has a tremendous impact on charge transport in crystalline compounds on the pseudo-binary line between Sb2Te3 and GeTe. Directly after crystallization, the pronounced disorder on the cation sublattice renders crystalline Ge1Sb2Te4 - a composition with a carrier density of the order of 1020 cm-3 - an Anderson insulator. Annealing, however, induces the reduction of disorder and eventually triggers an insulator-to-metal transition. This study presents data on the electrical properties, the optical conductivity, and structural properties of the pseudo-binary compositions between Ge3Sb2Te6 and GeTe. In contrast to the preceding investigations, which rely on the annealing temperature for tuning the electrical properties, this study elucidates the impact of stoichiometry and demonstrates that the stoichiometry may be employed as an alternative control parameter for the metal-to-insulator transition. The combination of annealing temperature and stoichiometry, therefore, provides a rich playground for tailoring disorder and, as a consequence, the transport of charge. Disorder-induced insulator-to-metal transitions govern the charge transport in the crystalline states of the pseudo-binary GeTe-Sb2Te3 compounds. In contrast to former investigations, which rely on the annealing temperature for controlling the degree of disorder, this work explores the impact of stoichiometry and demonstrates that the stoichiometry can be employed as an alternative control parameter for the metal-insulator transition.