Ultralow-power switching via defect engineering in germanium telluride phase-change memory devices

Crystal–amorphous transformation achieved via the melt-quench pathway in phase-change memory involves fundamentally inefficient energy conversion events; and this translates to large switching current densities, responsible for chemical segregation and device degradation. Alternatively, introducing defects in the crystalline phase can engineer carrier localization effects enhancing carrier–lattice coupling; and this can efficiently extract work required to introduce bond distortions necessary for amorphization from input electrical energy. Here, by pre-inducing extended defects and thus carrier localization effects in crystalline GeTe via high-energy ion irradiation, we show tremendous improvement in amorphization current densities (0.13–0.6 MA cm −2 ) compared with the melt-quench strategy (∼50 MA cm −2 ). We show scaling behaviour and good reversibility on these devices, and explore several intermediate resistance states that are accessible during both amorphization and recrystallization pathways. Existence of multiple resistance states, along with ultralow-power switching and scaling capabilities, makes this approach promising in context of low-power memory and neuromorphic computation. Phase change memories involve crystalline-to-amorphous transformations which require high current densities. Here, the authors introduce extended defects in GeTe crystals, reduce the current densities necessary for amorphization and obtain low-power, scalable memories with multiple resistance states.