Wet oxidation of AlGaAs: the role of hydrogen

Abstract

Wet oxidation of AlGaAs to form Al2O3 by the reduction of H+ from water to H produces intermediate As2O3. Reduction of As2O3 by H to elemental As enables the escape of arsenic from the oxidized film. Further reduction of As to AsH3 can provide another volatile As species. Formation of intermediate As is problematic for the use of wet oxidation in metal-insulator-semiconductor applications. The kinetic balance between As2O3 formation and As escape can explain the transition between the linear and parabolic time dependence of the wet oxidation of buried AlGaAs layers. The near-total suppression of wet oxidation by O2 is attributed to the suppression of volatile product formation through consumption of atomic hydrogen by reaction with O2 to form H2O in preference to the hydrogen reduction of As2O3.