On the kinetics of the anodic oxidation of GaP

The formation of anodic oxides on n-GaP were studied by means of neutron activation analysis measuring the P-32 activity in the film and in the solution. The oxide film formation under potentiostatic conditions and the competing oxide dissolution during film formation and under currentless conditions were investigated. The best description of the oxide growth is a combination of the parabolic growth law for film formation and of a zeroth order process for the simultaneous film dissolution. The rate constant for film formation linearily depends on the square of the applied voltage. The dissolution rate also increases with increasing the applied voltage. The dissolution rate of oxide films decreases under currentless conditions compared with dissolution during growth.