Properties of GaP(001) surfaces treated in aqueous HF solutions

type:Journal Article
Chemically cleaned GaP(001) surfaces in aqueous HF solutions have been studied using\nspectroscopic ellipsometry (SE), ex situ atomic force microscopy (AFM), x-ray photoelectron\nspectroscopy (XPS), wettability, and photoluminescence (PL) measurements. The SE data clearly\nindicate that the solutions cause removal of the native oxide film immediately upon immersing the\nsample (?1 min). The SE data, however, suggest that the native oxide film cannot be completely\netch-removed. This is due to the fact that as soon as the etched sample is exposed to air, the oxide\nstarts to regrow. The SE estimated roughness is ～1 nm, while the AFM roughness value is\n～0.3 nm. The XPS spectra confirm the removal of the native oxide and also the presence of regrown\noxide on the HF-etched GaP surface. The wettability measurements indicate that the HF-cleaned\nsurface is hydrophobic, which is in direct contrast to those obtained from alkaline-cleaned surfaces\n(hydrophilic). A slight increase in the PL intensity is also observed after etching in aqueous HF solutions.