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

The GaAs(100) surfaces chemically treated in HCl-isopropanol solution and a nnealed in vacuum were studied by means of Auger electron spectroscopy, x-r ay 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. T he HCl-isopropanol treatment removes gallium and arsenic oxides from the su rface, with about 2 monolayers of excess arsenic being left on it. The resi dual carbon contaminations were around 0.2-0.4 ML and consisted of the hydr ocarbon molecules. These hydrocarbon contaminations were removed from the s urface together with the excess arsenic by vacuum annealing at 300-420 degr ees C. With increased annealing temperature, a sequence of six reconstructi ons were identified by LEED: (1 X 1), (2 X 4)/c(2 X 8), (2 X 6), (3 X 6), ( 4 X 1) and c(8 X 2) in the temperature intervals of 250-400, 420-480, 480-5 00, 500-520, 520-560 and 560-600 degrees C, respectively. All surface recon structions were irreversible. The structural properties of chemically prepa red GaAs(100) surfaces were found to be similar to those obtained by molecu lar-beam.epitaxy-growth and by decapping of As-capped epitaxial layers. (C) 1999 American Vacuum Society. [S0734-2101(99)029057-X].