Homogeneous phase W-Ge-Te material with improved overall phase-change properties for future nonvolatile memory

Homogeneous phase W-Ge-Te material has been proposed and investigated for phase-change memory (PCM) applications. The crystallization temperature of GeTe is markedly improved by introducing W atoms. In the W-Ge-Te material, W atoms bonding to Ge and Te atoms serve as substitutional impurities. During the crystallization process, the diffusion of Ge and Te atoms is restricted by W atoms that have larger atomic mass, which further leads to more uniform crystallization of the material. W atoms serve as nucleation centers and attract the surrounding Ge and Te atoms, quickly building crystal grains. W _0.1(GeTe)_0.9 film has a 10-year data retention temperature of 225 °C and an ultrafast crystallization time of 3 ns. Specifically, W_0.1(GeTe)_0.9 film can withstand the Pb-free solder reflow temperature (260 °C) for 4.6 × 10⁴ s. A voltage pulse of as little of 10 ns long can realize reversible operations for W _0.1(GeTe)_0.9-based PCM devices. In addition, good endurance (5 × 10⁵ cycles) has also been obtained for the cell.