Investigation of special features of parameters of Schottky barrier contacts caused by a nonlinear bias dependence of the barrier height

Abstract

The results of studying the IV-characteristics (IVCs) of the contact Au-n-GaAs obtained by electrochemical deposition are presented. The observed characteristics - the bias dependence of the ideality factor (n), the measured (ϕbm) and effective (ϕbI) barrier heights, an inverse relationship between the measured barrier height and ideality factor, and the edge effects (the dependence of n, ϕbm, and ϕbI on the contact diameter) are explained by the nonlinear bias dependence on the effective barrier height. The explanation is given on the basis of the contact model with an intermediate layer and interface states (Bardeen model), and the intimate contact model with the subsurface states. The nonlinearity of the bias dependence on the barrier height is due to the inhomogeneous energy distribution of the interface states (a decrease in density from the edges to the middle of the bandgap) and the inhomogeneous energy and coordinate (from the surface to the depth) distribution of the subsurface states. An essential feature for every model is also the condition that the barrier height and ideality factor are measured at a constant current (or in a constant range of currents) while studying contacts with different diameters or when measuring the IVCs at different temperatures. This condition is not difficult to achieve, but gives the necessary certainty to different barrier height values used in examining experimental results. Some limitations and shortcomings of the widely used model of inhomogeneous Schottky barrier contact with the “saddle points” are also discussed.