Engineering flexible germanium nanomembranes using porous germanium and graphene

Freestanding semiconductor membranes (FSMs) are attracting strong interest for their lightweight, flexible, and stackable properties, which enable novel device architectures and integration of high-performance III-V materials with silicon. This work introduces the Porous Germanium Efficient Epitaxial LayEr Release (PEELER) process, a scalable method for producing wafer-scale monocrystalline Ge nanomembranes with demonstrated substrate reuse. Using a nanoengineered porous layer, we achieve smooth (⪅1nm roughness), crystalline membranes compatible with III-V epitaxy. Importantly, the parent Ge wafer can be reconditioned and reused for multiple cycles, greatly reducing material consumption. As proof-of-concept, a solar cell was fabricated on a released Ge membrane, confirming both device-grade performance and practical applicability. PEELER offers a new pathway for sustainable, flexible, and stackable optoelectronics.