Disorder-Induced Localization in Crystalline Pseudo-Binary $GeTe-Sb_{2}Te_{3}$ Alloys between $Ge_{3}Sb_{2}Te_{6}$ and $GeTe$

Disorder has a tremendous impact on charge transport in crystalline compounds on the pseudo-binary line between $Sb_{2}Te_{3}$ and $GeTe$. Directly after crystallization, the pronounced disorder on the cation sublattice renders crystalline $Ge_{1}Sb_{2}Te_{4}$—a composition with a carrier density of the order of $10^{20} cm^{−3}$—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 $Ge_{3}Sb_{2}Te_{6}$ 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