Flat single crystal Ge membranes for sensors and opto-electronic integrated circuitry

A thin, flat and single crystal membrane on which to mount sensors is generally required for integration with electronics through standard silicon processing technology. We present an approach to producing single crystal membranes of germanium with in-built tensile strain, which serves to keep the membrane flat and ripple free, and demonstrate a 600 nm thick, free-standing 1 mm2 Ge membrane. We convert the fabrication technique into an integrated-circuit compatible wafer scale process to produce 60 nm thin membranes with large areas of 3.5 mm2. The single crystal Ge membrane provides an excellent platform for further epitaxial growth or deposition of materials.