Preparation of patterned GaAs structures for MEMS and MOEMS

The preparation and characterisation of four-sided GaAs pyramidal mesas is presented. A novel wet-chemical etching method uses a fast lateral etching of an AlAs interlayer that influences the cross-sectional profile of the structure. The sidewalls of the prepared pyramidal structures together with the (100) bottom facet formed the cross-sectional angles 25° and 42° for mask edges parallel, respectively, perpendicular to the {011} cleavage planes. For mask edges turned in 45° according to the cleavage planes, 42° cross-sectional angles were obtained. Using the method, more than 10-μm-high symmetric GaAs “Egyptian” pyramids with smooth tilted facets were prepared. The quality of the pyramidal structures was checked using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Structures are suitable for the following epitaxial overgrowth of quantum structures.