Effects of pH values on the kinetics of liquid-phase chemical-enhanced oxidation of GaAs

The liquid-phase chemical-enhanced oxidation technique has been demonstrated to be an effective means of growing stable native films on GaAs. The gallium-ion-containing solution results in a fairly high oxidation rate near room temperature. The pH value of the oxidation solution appears to be a dominant factor in the kinetics of oxidation. Due to the enhancement of Ga-containing cations in the solution, a window of initial pH values from approximately 4.0 to 4.5 is found to be the optimum pH range for oxide growth. The pH-incorporated mechanism provides consistent interpretations for the unusual experimental results such as etchback of oxide thickness and increase of refractive index. In addition, the results of the pH-controlled procedure confirms the proposed role of pH. According to secondary ion mass spectroscopy profiles, it is found that the increasing As/Ga ratio of the oxide film contributes to the increase of oxide refractive index.