Formation of three-dimensional GaAs microstructures by combination of wet and metal-assisted chemical etching

Previously, plasma-enhanced dry etching has been used to generate three-dimensional GaAs semiconductor structures, however, dry etching induces surface damages that degrade optical properties. Here, we demonstrate the fabrication method forming various types of GaAs microstructures through the combination etching process using the wet-chemical solution. In this method, a gold (Au)-pattern is employed as an etching mask to facilitate not only the typical wet etching but also the metal-assisted chemical etching (MacEtch). High-aspect-ratio, tapered GaAs micropillars are produced by using [HF]:[H2O2]:[EtOH] as an etching solution, and their taper angle can be tuned by changing the molar ratio of the etching solution. In addition, GaAs microholes are formed when UV light is illuminated during the etching process. Since the wet etching process is free of the surface damage compared to the dry etching process, the GaAs microstructures demonstrated to be well formed here are promising for the applications of III-V optoelectronic devices such as solar cells, laser diodes, and photonic crystal devices. ((c) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)