Wet oxidation of AlxGa1-xAs: Temporal evolution of composition and microstructure and the implications for metal-insulator-semiconductor applications

Three important processes dominate the wet thermal oxidation of AlxGa1-xAs on GaAs: (I) oxidation of AZ and Ga in the AlxGa1-xAs alloy to form an amorphous oxide, (2) formation and elimination of crystalline and amorphous elemental As and of amorphous As2O3, and (3) crystallization of the amorphous oxide film. Residual As can lead to strong Fermi-level pinning at the oxidized AlGaAs/GaAs interface, up to a 100-fold increase in leakage current, and a 30% increase in the dielectric constant of the oxide layer. Thermodynamically favored interfacial As may impose a fundamental limitation on the use of AlGaAs wet oxidation in metal-insulator-semiconductor devices in the GaAs material system. (C) 1997 American Institute of Physics.