Composition and structure of HCl-isopropanol treated and vacuum annealed GaAs(100) surfaces

The GaAs(100) surfaces chemically treated in HCl-isopropanol solution and annealed in vacuum were studied by means of Auger electron spectroscopy, x-ray photoelectron spectroscopy, high-resolution electron energy-loss spectra, and Low-energy electron diffraction (LEED). Chemical treatment and sample transfer into ultrahigh vacuum were performed under nitrogen atmosphere. The HCl-isopropanol treatment removes gallium and arsenic oxides from the surface, with about 2 monolayers of excess arsenic being left on it. The residual carbon contaminations were around 0.2–0.4 ML and consisted of the hydrocarbon molecules. These hydrocarbon contaminations were removed from the surface together with the excess arsenic by vacuum annealing at 300–420 °C. With increased annealing temperature, a sequence of six reconstructions were identified by LEED: (1×1), (2×4)/c(2×8), (2×6), (3×6), (4×1) and c(8×2) in the temperature intervals of 250–400, 420–480, 480–500, 500–520, 520–560 and 560–600 °C, respectively. All surface reconstructions were irreversible. The structural properties of chemically prepared GaAs(100) surfaces were found to be similar to those obtained by molecular-beam epitaxy-growth and by decapping of As-capped epitaxial layers.