Micro-fabrication and transfer of a detachable Ge epitaxial layer grown on porous germanium

Germanium (Ge) substrates are usually used for epitaxial growth of III- V materials but represent a significant part of the cell total cost. The lift-off technique using porosification by bipolar chemical etching is a promising approach to detach the active layers from the Ge substrate and allows Ge substrate reuse. However, this solution raises challenges concerning the delamination and possible structural deterioration of the mem-brane during the micro-fabrication of the solar cell. In this paper, we successfully apply the main micro-fabrication steps on a Ge membrane grown on porous Ge. The front side process using UV lithography and Au-Ni deposition for contacts has been successfully performed without membrane degradation. Those contacted membranes were also successfully transferred on a host substrate. X rays measurements (XRD) were also performed before and after detachment and shows no damage on the crystalline quality of Ge membrane.