Analysis of small-signal response of the SiO₂-(n) GaAs interface based on a surface disorder model

An attempt to clarify the frequency behaviour of the (n) GaAs-SiO₂ interface has been presented. Metal-SiO₂-GaAs structures with a PECVD-deposited insulator layer have been investigated. The measurements of capacitance-voltage characteristics at different frequencies as well as the frequency dependence of MIS capacitance and conductance at fixed gate voltages have been performed. A large frequency dispersion of MIS admittance has been revealed. The model of an insulator-semiconductor interface as a disordered system with localized electron states distributed in energy and in space can be used to explain the experimentally observed broad spectrum of time constants. The method of analysis of measured characteristics is based on a least-squares fitting of experimental data with theoretical dependencies allowed to determine the parameters of the interface states as well as some parameters of MIS structures.