A preliminary study of MIS diodes with nm-thin GaAs-oxide layers

Direct oxidation of GaAs wafers, by using UV and ozone oxidation system, wa s performed to form nm-thin GaAs-oxide layers. Composition of the oxidized layer, studied by XPS analysis, shows depth-dependent atomic percentage of the Ga, As, and O. Surface flatness and thickness of the oxide were investi gated with AFM. The oxide thickness is nearly proportional to square root o f the UV and ozone process time. Using the oxidized layer as the insulator, Ni/insulator/n-GaAs MIS diodes were fabricated, and compared with Ni/n-GaA s Schottky diodes of their gate leakage currents. Very clear leakage curren t suppression effect of the insulating layer is observed, which is controll able by controlling the UV and ozone process time. However, the suppression effect is much smaller than that theoretically estimated for a MIS diode w ith perfectly uniform SiO2. Theoretical equations to estimate effect of a n m-thin insulating layer on current-voltage relation of a MIS diode are show n in the appendix. (C) 1999 Elsevier Science Ltd. All rights reserved.