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Currently, III-V multijunction solar cells holds the highest efficiency. However, they are expensive to produce and this prevents their large-scale use. For single GaAs solar cells, most of the total cost of the cell comes from the substrate. For III-V cells on Ge substrate, the thickness of the substrate is usually between 150 μm and 180 μm, whereas only 1 μm would be sufficient to maintain the performance of the cell. Moreover, 95% of the weight of the cell comes from the substrate which is a problem for the space domain. It is therefore necessary to find an economical and reliable approach for layer separation and reuse of Ge substrate. The approach proposed in this work shows the epitaxial growth of high-quality monocrystalline Germanium template on a 4-inch porous Ge substrate. The porous layer reconstruction leaves voided interface with nanometer scale pillars allowing defect free detachment of the epitaxial …