Tuning Crystallization Pathways in Ge-Rich GST Alloys: The Influence of Nitrogen and Hydrogen

Abstract

This study investigates the effects of nitrogen and hydrogen doping on the crystallization mechanisms of Ge-rich GST (GGST) alloys, widely used in phase-change memory applications. Using in situ synchrotron X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy, and thermal desorption spectroscopy, this article examines undoped, nitrogen-doped, and co-doped (N + H) GGST samples to understand their structural and kinetics transformations during thermal treatments. Nitrogen doping significantly increases the crystallization temperature and enhances thermal stability, while reducing grain sizes and modifying kinetics. Hydrogen shows a contrasting effect. Alone, it minimally impacts crystallization temperatures but decreases activation energy and promotes heterogeneous nucleation, mediated by transient GeTe Pnma phase. However, combined with nitrogen, hydrogen disrupts the formation of Ge-N bonds, favoring N-H interactions instead. This suppresses nitrogen effects while introducing interface-driven crystallization mechanism. The findings provide new insight into dopant interactions within GGST alloys, demonstrating the potential of co-doping strategies to fine-tune phase change behavior. The study underscores the need for further exploration of dopant combinations to achieve enhanced stability and performance, particularly for memory devices operating in harsh environments.