Mesoporous germanium morphology transformation for lift-off process and substrate re-use

Abstract

The morphology of electrochemically formed mesoporous Ge double-layer and its transformations during ultra-high-vacuum annealing at 600–700 °C are investigated by scanning electron microscopy. It was found that the transformation occurs via mass transport at constant volume. The process transforms the pores into faceted spherical voids. These findings determine the optimal conditions for the transformation of the mesoporous Ge into a useful structure, which consists of a 1.8 μm thick monocrystalline Ge film with buried lateral cavities allowing for subsequent lift-off. The monocrystalline nature of the film and its suitability as a seed layer for GaAs epitaxy are demonstrated by X-ray diffraction.