Influence of sulfur on the Sb-GaAs(001) interface

The modification of clean GaAs(100) surfaces by in situ deposition of molecular sulfur was investigated by soft X-ray photoemission spectroscopy. Upon sulfur treatment of the clean GaAs(001) sample at 500 degrees C in ultra-high vacuum the formation of an approximately 0.3 nm thick gallium sulfide-like compound is observed that exhibits a (2 x 1) LEED pattern. Owing to the sulfur modification on n-GaAs a reduction of the band bending by 0.44 eV is achieved, whereas the band bending on p-GaAs is increased by 0.12 eV. Antimony was deposited onto these sulfur-modified surfaces from a Knudsen cell. This was found not to react with the gallium sulfide layer on the surface. At approximately 1.8 nm antimony coverage the position of the Fermi level above the valence band maximum amounts to 1.05 eV and 0.66 eV for n- and p-doped samples respectively, which is higher than the Fermi level position observed for the unmodified Sb-GaAs(001) Schottky contact (0.75 eV and 0.50 eV). The change in barrier height due to the sulfur passivation is attributed to a sulfur-induced interface dipole. (C) 1999 Elsevier Science B.V. All rights reserved.