‘There and Back Again’: Reusable Germanium Wafers with Ge-on-Nothing Structures for Triple-Junction Solar Cells

Germanium-on-Nothing is proposed as a lift-off method to fabricate thin and lower-cost germanium templates for multijunction solar cells. This contribution presents how such foils, that are thickened epitaxially, can replace bulk wafers as III-V epitaxy seed, mechanical support, and bottom solar cell junction. Furthermore, by detaching large-area foils from reconditioned wafers, it demonstrates that the starting germanium wafer can be re-used and the recycling loop closed.