Tapered GaAs quantum wells and selectively contactable two-dimensional electron gases grown by shadow masked molecular-beam epitaxy

We report on the use of shadow masks for the growth of GaAs quantum wells with spatially varying thicknesses. Using cathodoluminescence we observe a clear shift of the luminescence energy as a function of the lateral position. Combining masked and directional epitaxy, the quantum wells can be both laterally and vertically patterned. This way, stacked, two-dimensional electron gases are realized which can be selectively contacted without the use of complicated in-situ or post-growth patterning techniques. The quality of the epitaxial material grown through the openings of the masks is investigated by optical and electrical characterization.