Arsenic Formation on GaAs during Etching in HF Solutions: Relevance for the Epitaxial Lift-Off Process

Abstract

The epitaxial lift-off (ELO) process is utilized to produce thin-filmIII-V devices, while the substrate (GaAs wafer) on which the III-Vstructure was grown can be reused. However, so far the direct reuseof these GaAs wafers is inhibited by the remnants on the wafer surfacethat cannot be removed in a straightforward fashion utilizing generalcleaning methods. Therefore, etching of GaAs wafers in hydrofluoricacid was investigated by microscopic techniques, profilometry andX-ray photoelectron spectroscopy. It was found that immediately afteretching the wafer surface is covered by a brown layer of elementalarsenic. The thickness and uniformity of this layer depend on bothillumination during etching and the HF concentration. During storageof the etched wafer the As layer is replaced by As2O3 particles.It is shown that oxide particles form only when the wafer is exposedto light in the presence of air. A model that explains the As formationand the subsequent particle formation is given. (C) 2012 The ElectrochemicalSociety.