Monolithic fabrication of 1S1R cross-point device using single Ge_xTe_1-x material by controlling composition between...

Three-dimensional (3D) integrated one-selector one-resistor (1S1R) cross-point arrays are emerging as a leading next-generation memory technology. Achieving both nonvolatile memory switching and volatile threshold switching within a single material system offers tremendous potential for simplifying fabrication. This study demonstrates that the memory and threshold switching behavior of germanium-telluride (Ge_xTe_1-x) devices can be precisely tuned by controlling their atomic ratio. In the Te-deficient Ge_xTe_1-x system, the device exhibits nonvolatile memory switching with fast operating speed. Conversely, the Te-rich system functions as an excellent bidirectional selector for high-density memory applications, exhibiting high selectivity (> 10⁴) and a short delay time (< 55 ns). Material analyses using X-ray photoelectron spectroscopy and Raman spectroscopy reveal that these distinct electrical behaviors are driven by composition-dependent changes in the atomic structure. Furthermore, the fully integrated 1S1R stack demonstrates robust SET/RESET switching characteristics, maintaining a stable memory window of 0.2 V and an on/off current ratio exceeding two orders of magnitude (~ 1.12 × 10²). Notably, this integrated configuration provides superior operational reliability and enhanced endurance (~ 8 × 10⁶ cycles) compared to standalone phase-change memory devices. By elucidating these underlying mechanisms, this work reduces the fabrication complexity of stackable devices and opens up wide-ranging applications for unified memory and selector systems.