Fabrication of nanoscale single crystal InP membranes

The authors have developed a process for fabricating fully enclosed single crystal InP freestanding membranes using entirely front side processing. A multilayer lattice matched InP∕InGaAs heterosystem incorporating a 500Å membrane layer was grown by molecular beam epitaxy followed by two step surface patterning, first for the support structure and then for the membrane structure definition. Membranes with lateral dimensions ranging from 1to10μm have been fabricated using optical and electron beam lithography. The process is easily scalable, limited only by the ability of the membrane layer to act as an effective etch stop, i.e., ∼30Å.