Kinetics of GaAs Plasma Anodization

Abstract

The kinetics of plasma anodization at constant total current have been studied. The plasma source is a multipole (hot cathode associated with a magnetic confinement). The results show a decrease of the growth rate as the oxide thickness increases, in contrast with wet anodization at constant total current. The presence of unoxidized arsenic in the bulk and at the oxide semiconductor interface, which is characteristic of plasma grown oxides, does not seem to have a significant influence on the kinetics. An ion space charge which can modify the ratio of the electronic and ionic currents during the growth can account for the observed kinetics. Satisfactory agreement is obtained by using a very simplified space charge model. The calculations give order of magnitude of phenomenological ion “migration” (i.e., field aided diffusion, etc.) coefficients which are much larger than usual diffusion coefficients.