GaAs and InP surface behaviour under ion bombardment, alkali deposition and oxygen exposure

A detailed investigation of the GaAs and InP (110) surface modification by Ar+ bombardment and by exposure to alkali metal flux and/or oxygen atmosphere has been performed. The ion beam processed surfaces have been found to be metal enriched over the extent of the ion penetration region, however in GaAs the As concentration is larger in the outmost surface layer with respect to the subsurface one. The kinetics of the alkali metal-semiconductor interface formation presents similar characteristics for Cs, K and Na deposition, on both GaAs and InP, either cleaved or sputtered processed. The oxidation rate of these interfaces is enhanced several orders of magnitude with respect to the clean surfaces, and it is strictly related to the amount of metal. The oxidation efficiency increases linearly up to a metal fractional coverage x = 0.7. Above this coverage the promotion effect saturates. (author)