Understanding and Circumventing Failure Mechanisms in Chalcogenide Optical Phase Change Material Ge ₂ Sb ₂ Se ₄ Te

Chalcogenide optical phase change materials (PCMs) have garnered significant interest for their growing applications in programmable photonics, optical analog computing, active metasurfaces, and beyond. Limited endurance or cycling lifetime is however increasingly becoming a bottleneck toward their practical deployment for these applications. To address this issue, a systematic study elucidating the cycling failure mechanisms of Ge 2 Sb 2 Se 4 Te (GSST) is performed, a common optical PCM tailored for infrared photonic applications, in an electrothermal switching configuration commensurate with their applications in on‐chip photonic devices. Further a set of design rules building on insights into the failure mechanisms is proposed, and successfully implemented them to boost the endurance of the Ge 2 Sb 2 Se 4 Te (GSST) device to over 67 000 cycles.