Formation of GaAs three-dimensional objects using AlAs “facet-forming” sacrificial layer and H3PO4, H2O2, H2O based solution

We propose here that sacrificial layers used in III–V technology can be utilized also as “facet-forming” sacrificial layers if the lateral etching rate of the embedded layer is close to the vertical etching rate of the basic material. The idea is supported by computer simulations as well as by several experiments in which high and smooth GaAs mesas with controlled shape and tilt were formed. The wet-chemical etching method uses H3PO4, H2O2, and H2O based solution and an AlAs layer embedded into GaAs. The AlAs layer controls the lateral etching rate and influences the cross-sectional profile of GaAs three-dimensional objects. We show that the mesa slope can be precisely tuned via the solution composition, AlAs thickness, and etching depth. The method suppresses the influence of the GaAs crystallography on the final mesa shape, which simplifies its epitaxial overgrowth. The mesa sidewalls obtained are smooth enough for epitaxial growth of nonplanar heterostructures for microelectromechanical systems and for nanoelectronics.