Multilevel data storage in multilayer phase change material

Superlattice-like GaSb/Sb₄Te phase change film was proposed for multilevel phase change memory with the feature of three stable resistance states. Two distinct transition temperatures of around 170 and 230 °C were observed in the superlattice-like GaSb/Sb₄Te thin film. Under elevated temperature, the precipitated rhombohedral Sb phase was found in the Sb₄Te layer, which was followed by the crystallization of rhombohedral Sb₂Te₃, whereas the GaSb layer remained almost in the amorphous state except the impinged Sb grains. The formation of percolation path for crystallization in the GaSb layer can account for the multilevel resistance states. For the GaSb/Sb₄Te-based device, the reversibly electrical switching was realized under the electrical pulse as short as 10 ns, and the endurance was achieved at least 10⁵ cycles among different resistance states.