Coordinated sub-cycle modulation atomic layer deposition of atomically homogeneous GeTe9 thin films for high-performance OTSs

Abstract

In this information era, the escalating demand for memory, coupled with the emergence of three-dimensional (3D) memory architectures, has made the suppression of leakage current in high-density arrays a critical challenge. The ovonic threshold switch (OTS) is a key component of 3D phase-change memory (PCM), and Te-rich OTS materials are highly promising due to their low threshold voltage and fast switching speed. Te-rich chalcogenides are promising OTS materials due to their low threshold voltage and fast switching speed. However, using conventional atomic layer deposition (ALD) it is highly challenging to achieve sufficient atomic intermixing in these high-Te-content materials, often resulting in phase separation and compromised device performance. This study introduces a coordinated sub-cycle modulation (CSM) strategy to overcome this barrier. By synchronizing the GeTe/Te sub-cycle ratio with interfacial diffusion kinetics, we achieved the ALD of GeTe₉ films with atomic-level homogeneity and an amorphous structure. The fabricated OTS devices demonstrate outstanding integrated performance: a high off-state resistance of 10⁷ Ω, an ultra-fast switching speed of 4 ns, and excellent cycle endurance exceeding 10⁹ cycles. This study not only provides a viable selector solution for 3D memory but also establishes CSM as a generalizable paradigm for synthesizing extreme-ratio, non-stoichiometric functional materials via ALD.