FERMI-LEVEL VARIATION ON GAAS(110) SURFACE WITH SB OVERLAYER STUDIED WITH A PHOTOELECTRON MICROSCOPE

Bare and Sb covered GaAs(110) surfaces were studied with a photoelectron microscope. For the cleaved surfaces, maximum band bendings of 0.85 and 0.50 eV was observed for n- and p-type GaAs, respectively. For n-type, evaporation of Sb reduces the band bending from 0.85 to 0.55 eV. Annealing p-GaAs at 350-degrees-C almost restored the flatband condition for an initially unpinned area. A reduction of band bending was observed for an initially heavily pinned area. This suggests that the cleavage defects originate partly from surface strain which can be removed by relaxing the strain with the formation of an ordered Sb overlayer. Sb desorbs from the GaAs surfaces when annealed at 560-degrees-C. The Fermi level on this surface is at 0.35 eV above the valence-band maximum regardless of initial band bending conditions. The new surface is attributed to the destructive process of Sb desorption.