Electrical properties of SiO2-(n) GaAs interface on the basis of measurements of MIS structure capacitance and conductance

The Au/Pd/Ti-SiO2-GaAs structures with PECVD deposited insulator layers hav e been investigated. The (100) oriented n-GaAs wafers with and without (NH4 )(2)S surface treatments have been used. The measurements of capacitance-vo ltage characteristics at different frequencies as well as the frequency dep endence of MIS capacitance and conductance at fixed gate voltages have been performed. The large frequency dispersion of MIS admittance has been obser ved. The model of insulator-semiconductor interface as disordered system wi th localized electron states distributed in energy and in space offers the possibility of an explanation of the experimentally observed broad spectrum of time constant. It has been stated that sulfur treatment of GaAs surface introduces the negative fixed charge at SiO2-GaAs interface rather than re duces the density of interface states. (C) 1999 Elsevier Science S.A. All r ights reserved.