Multidielectrics for GaAs MIS devices using composition-graded Al _xGa_1-xAs and oxidized AlAs

Metal-insulator-semiconductor (MIS) structures were prepared by dry thermal oxidation of an AlAs layer that had been grown on a composition-graded Al _xGa_1-xAs layer on GaAs. The epitaxial layers were grown by molecular beam epitaxy. Capacitance-voltage (C-V) measurements of these MIS structures demonstrated the achievement of inversion behavior with essentially no hysteresis and flatband voltages ranging from 0 to 0.1 V, which correspond to a fixed interface charge density of less than 2×10¹⁰ cm ^-2. It was also found that the stress developed between the oxide film and the epilayer was reduced in these MIS structures.