The macroscopic electronic behavior and atomic arrangements of the GaAs surfaces immersed in HCI solution were studied by surface current transport (SCT), band-edge photoluminescence (PL), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS). SCT measurements indicated reduction of the surface band bending on immersion into HCI solution for both n- and p-type materials. A remarkable increase of the band-edge PL intensity was also observed. In the AFM image taken in HCI solution, the (001) surface showed an array of atoms along [110] and [110BAR] direction with the spacing of 4.1 angstrom, indicating presence of a (1 X 1) structure. Similarly, (1 X 1) images with threefold symmetry were observed on the (111)A and (111)B surfaces. The XPS analysis of the GaAs surfaces after immersion into HCI solution detected a monolayer level presence of gallium chloride. These results indicate that bond termination on the GaAs surface by adsorption of Cl atoms. to surface Ga atoms realizes a nonstrained regular (1 X 1) passivation structure which removes surface states from the band-gap region.