Chemical etching characteristics of GaAs(100) surfaces in aqueous HF solutions

Chemical etching characteristics of GaAs(100) surfaces in aqueous HF soluti ons have been studied using spectroscopic ellipsometry (SE), atomic force m icroscopy (AFM), X-ray photoelectron spectroscopy (XPS), and wettability me asurements. The SE data clearly indicate that the HF solutions cause the ef ficient removal of the GaAs native oxide upon immersing the samples in the solutions. When the native oxide is completely etch-removed, the resulting surface has a roughened overlayer about 1.3 nm thick, which is about five t imes as large as the AFM rms value (similar to0.2-0.3 nm). The discrepancy of this is due to the SE technique being sensitive: to both the surface mic roroughness and the adsorbed chemical species, but AFM is sensitive only to the surface microroughness. The XPS data reveal that etching in the concen trated (50 wt %) solution selectively removes gallium while leaving element al arsenic on the GaAs surfaces. The XPS data also indicate the presence of fluorine on the HF treated surfaces. The as-degreased surface is hydrophil ic, while thr W-treated surfaces are highly hydrophobic. (C) 2000 The Elect rochemical Society. S0013-4651(00)03-122-0. All rights reserved.