Ultrasmall-volume-change chalcogenide for performance improvement of phase-change memory

A huge internal stress is usually induced by a volume change in chalcogenide as the storage media in phase-change memory (PCM) devices and deteriorates their performance. In this work, doping N into GeTe with a fast operation speed (ns order) is investigated with the aim of reducing the volume change upon crystallization. The volume change upon crystallization of an N-doped GeTe film is almost zero when N is doped in an appropriate amount. Cracks resulting from the stress caused by volume change disappear and the mean crystal size decreases by more than 50% upon N doping into GeTe. The behavior of the ultrasmall volume change allows the greatly improved performance of PCM.