Developing GeSbTe Superlattice Through Understanding of the Reversible Phases and Engineering Its Interspaces

Abstract

Interfacial phase‐change materials (iPCM), which are alternatively stacked with GeTe and Sb2Te3 in the superlattice structure, have been highlighted as next‐generation PCM with improved overall phase‐change characteristics. However, several studies have reported that a melt‐quenching process, whereby the initial superlattice structure is not maintained within the reversible switching process, rather than the initially proposed melting‐free phase‐change mechanism, occurs during operation. Herein, GeSbTe superlattices are synthesized using molecular beam epitaxy, and the reversible phases of the superlattice obtained by irradiation with an optical pulsed laser (KrF; 280 nm, 25 ns) and re‐annealing or by applying different electrical pulses are investigated through careful structural analyses. The results revealed that Te atoms are aligned parallel to the interface regardless of the reversible phase, whereas cations and inherent vacancies are distributed differently during the phase‐change process. The stability of memory cells with cycling operations can be enhanced by enriching inherent vacancies, and the switching energy can be reduced by expanding the interspaces via doping engineering.