Composition-Driven Optimization of Amorphous Ge1-xSex for High-Performance OTS Selectors

Abstract

To address the demand for high-density three-dimensional phase-change memory, GeSe-based ovonic threshold switching (OTS) selectors have garnered significant attention for their favorable thermal stability and integrability. In this work, we systematically investigate the structural, electronic, and migration properties of amorphous Ge_1-xSe_x (x = 0.2, 0.4, 0.6, 0.8) using first-principles molecular dynamics simulations. Our results reveal that intermediate compositions (x = 0.4, 0.6) enhance the stability of the amorphous structure through the formation of a network dominated by heteropolar Ge--Se bonds with octahedral-like coordination. The band gap is shown to increase nearly linearly with Se content, measuring 0.58 eV, 0.73 eV, and 0.81 eV for x = 0.4, 0.6, and 0.8, respectively, providing a basis for tuning the threshold voltage via composition. Furthermore, the suppressed atomic diffusion observed in these intermediate compositions helps retard crystallization and phase separation, thereby improving the cycling endurance of devices. Our atomic-scale analysis clarifies how composition tailors the properties of amorphous GeSe systems, paving the way for the design and application of high-performance, environmentally benign OTS selectors.