Large-area plan-view sample preparation for GaAs-based systems grown by molecular beam epitaxy.

We describe a method for plan-view transmission electron microscopy (TEM) sample preparation that takes advantage of extreme etch-rate selectivity in GaAs and AlAs in HF/H2O solutions. GaAs/InxGa1-xAs/GaAs strained-layer films (x = 0.05, 0.10, 0.19, 0.22) were chemically lifted off using this technique and were mounted on Cu TEM grids such that TEM transparent areas of up to 1 x 2 mm of constant thickness (196.4 nm) could be viewed. This simple, large-area plan-view technique uses only chemical methods and significantly extends the usefulness of TEM for the evaluation of crystal quality in GaAs-based epitaxial systems. The method requires the growth of a release layer of AlAs (10 nm thick) prior to the layered structure of interest.