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 fo rm an amorphous oxide, (2) formation and elimination of crystalline an d amorphous elemental As and of amorphous As2O3, and (3) crystallizati on of the amorphous oxide film. Residual As can lead to strong Fermi-l evel pinning at the oxidized AlGaAs/GaAs interface, up to a 100-fold i ncrease in leakage current, and a 30% increase in the dielectric const ant of the oxide layer. Thermodynamically favored interfacial As may i mpose a fundamental limitation on the use of AlGaAs wet oxidation in m etal-insulator-semiconductor devices in the GaAs material system. (C) 1997 American Institute of Physics.