GPO/GaAs(0.5)P(0.5) MOS Capacitors.

Abstract : This report presents the results of a program to investigate the surface passivation properties of a dielectric thermally grown on GaAs(0.5)p(0.5). Oxide films were grown at 700 C in dry oxygen. Ion microprobe analysis of the oxide composition indicates that the bulk of the oxide is arsenic deficient and that there is an arsenic-rich insulator-semiconductor interface region. Current-voltage characteristics showed a Frenkel-Poole type of conduction with a transient behavior due to electron trapping. Dielectric strength averaged 1.75 x 10 to the 6th power V/cm for unannealed films. Depletion-type C-V characteristics were observed, and are a result of the low minority carrier generation rate in the wide bandgap GaAs(0.5)P(0.5). Hysteresis in the C-V characteristics is attributed to electron trapping in states which are not in equilibrium with the bias sweep voltage. The static dielectric constant of the oxide was determined to be 6.3 from the C-V characteristics. Interface trap density in the upper portion of the bandgap was determined to be about 8 x 10 to the 11th power per sq cm per eV using the capacitance differentiation method. A significant illumination effect on this trapping behavior was observed due to emptying of electron traps. Interface analyses based on conductance-voltage data were inconclusive because existing analytical models are apparently not adequate for III-V compound MOS interfaces. (Author)