Behavior of Al on Clean and Oxidized GaAs(110) Surfaces

The adsorption of Al on clean and oxidized GaAs(110) surfaces was studied. The characteristics of an oxide surface formed in vacuum and during the chemical etching process of the tip have been investigated using the field desorption (FD) cleaning method and the retarding potential analyzer (RPA) equipped with an argon laser. The results obtained for the FD clean surface and on the oxidized surface are discussed in terms of the RPA threshold and work function change. The oxide films formed at relatively low temperatures on the GaAs(110) surface can easily be desorbed by FD. The intrinsic potential drops across the oxide surface disappear suddenly at a certain field value. This may indicate that the desorbed surface region is composed of a metallic species such as Ga. Changes in work function are observed but there is no change in the threshold values (V th) with deposition of Al on the field-desorbed clean surface. The thick layers of Al on the oxidized surface completely cancel the effect of oxide on V th, which decreases to the value of a metallic clean surface. In addition, the value of V th decreases dramatically to that of a metallic clean surface by absorption of the laser beam on the oxidized surface, whereas only the thermal effect is seen on a metallic clean surface.