Non-volatile reflective displays based on ultrathin GeTe phase-change layers

Phase-change materials provide a promising approach for reflective displays with persistent optical states. However, single-layer devices often face challenges in simultaneously achieving high optical contrast, reliable phase stability, and effective primary-color generation. Here, rather than proposing a new cavity topology, we use the established Pt/ITO/PCM/ITO asymmetric Fabry-Pérot configuration as a controlled platform to establish design rules for a single fixed-thickness PCM active layer. This objective differs from the dual-GeTe reflector reported in Ref. [Adv. Opt. Mater.7, 1801214 (2019)], which employed two GeTe layers with thickness-dependent crystallization temperatures to enable selective switching and multiple color states using a single heater. By comparing GST, GeTe, and Sb₂Te₃ under identical optical boundary conditions, we evaluate the combined effects of phase-change modulation, optical loss, usable ultrathin thickness range, and reported phase stability. Layer-resolved absorption and electric-field analyses further distinguish the functions of the PCM and the bottom ITO spacer. Together, these findings establish a transferable design sequence: select the PCM according to the modulation-loss-stability trade-off, determine its thickness by balancing optical-field interaction against dissipative loss, and then tune the spacer optical thickness to position the desired spectral channel. Following this sequence, GeTe was selected for the present devices under the investigated conditions.