Alkali (K)/GaAs(1 1 0) interface: structure and oxygen reactivity

By means of Auger electron spectroscopy and direct recoil spectroscopy we have studied the growth of an alkali (K) overlayer on the GaAs(1 1 0) surface, the oxidation process of this system for different K coverages, and the temperature dependence of the desorption process for the K overlayer and oxide film. For low coverages, we found that the K atoms adsorb preferentially close to the Ga atoms, they also bond to As atoms for larger coverages. On the contrary, the oxygen adsorption is produced close to the As atoms for low K coverages. The annealing of the interface produces a preferential desorption of the K atoms. The final situation, previous to the oxide decomposition, is however characterized by the presence of K contaminants.