We present recent results of synchrotron radiation photoelectron spectroscopy, ultra-violet photoelectron spectroscopy, low energy electron diffraction, scanning tunneling microscopy, and photoluminescence measurements for the horizontal Bridgman-grown GaAs(001) surface prepared by the deoxygenated and deionized water (DODIW) treatment. We discuss the relationship between surface stoichiometry, surface structure, and the pinning position of surface Fermi level for the DODIW-treated GaAs(001) surface, and point out that the position of surface Fermi level is strongly affected by crystal defects near the surface.