Germanium Layer Transfer with Low Temperature Direct Bonding and Epitaxial Lift-off Technique for Ge-based monolithic 3D integration

We demonstrated high-quality single crystal Germanium (Ge) layer transferred on arbitrary substrates, such as Si, glass, and flexible plastic substrates utilizing direct bonding and epitaxial lift-off (ELO) techniques. Owing to Ge epitaxial growth on GaAs substrates with AlAs release layer, we successfully transferred epitaxial Ge layers on arbitrary substrates with a wide range of thickness from several um to $\sim 1$ nm. This layer tranfer approach enables us to realize Ge-based monolithic 3D devices without degradation of Ge crystalline quality.