Recrystallized germanium films on ceramics and other materials can serve as a low-cost replacement for the single-crystal germanium wafers currently used for high-efficiency III-V semiconductor solar cells. Related work implies that Ge films with large-grain sizes (> I mm) formed on thermal-expansion matched substrates, such as sintered alumina ceramic, would function as suitable alternative substrates for epitaxy of high-performance GaAs-based solar cells. For this purpose, we describe a process wherein Ge layers, 0.5-5 mum thick, are deposited by close-spaced vapor transport or sputtering on sintered alumina ceramics, fused silica, or thermally oxidized polysilicon substrates, capped with metal layers deposited by electron-beam evaporation, and recrystallized in an annealing step. Post-growth, the metal cap is stripped with a selective liquid etchant. Recrystallized Ge films have large (1-5 mm) grains and highly oriented textures. These structures provide suitable substrates for epitaxy of GaAs solar cells. (C) 2002 Elsevier Science B.V. All rights reserved.