Phase transition characteristics of nitrogen-doped antimony-telluride (N-Sb₂Te₃) thin films for a phase change random access memory

Nitrogen-doped Sb₂Te₃ films were prepared and their electrically induced phase transition properties were characterized. As-deposited and undoped Sb₂Te₃ films exhibited a crystalline phase and a low resistivity (∼1 Ω-cm) even at room temperature while the resistivity of the N-doped Sb₂Te₃ films that were used in the amorphous state increased to over 100 Ω-cm. It was revealed that N-doping could effectively increase the crystallization temperature and at the same time suppress grain growth. The amorphous Sb ₂Te₃ films doped with nitrogen were transformed into a crystalline phase by thermal annealing, resulting in a decrease in the resistivity by four orders of magnitude. To characterize N-doped Sb ₂Te₃ films, we adopted both the threshold switching behavior and the rapid and reversible resistance changes by means of the static DC bias sweep and electrical pulses, respectively. Since the resistance ratio of N-doped Sb₂Te₃ films induced by pulse injection is about a hundred times, N-doped Sb₂Te₃ films seem to be promising for phase change random access memories.