Investigation of the possibilities of the 'saddle points' model for an explanation of anomalies in the characteristics of Schottky-barrier contacts

Numerical and experimental analyses of a model of a Schottky-barrier (SB) contact with barrier-height inhomogeneity in the form of 'saddle points' (the Tung model) [1] are carried out. On the basis of the known data for the contacts with Si, InP, and GaN and the experimental data obtained in this work for the Au-GaAs, Ni-GaAs, Ir-GaAs, and Pt-Rh-GaAs contacts, it is shown that the approximation widely used in the literature for the ideality factor of the I-V characteristics (IVCs) in the Tung model does not correspond to an exact solution, which, in turn, does not correspond to the real IVCs of contacts, at least at room temperature. The density of patches is demonstrated to have significant influence on the ideality factor under certain conditions, which is ignored by the Tung approximation. For the first time, on the basis of the known data on the distribution of the parameter gamma (sigma(gamma)), the spread of the barrier height (sigma(phi)) is simulated for a set of similar contacts. The results obtained indicate that the standard deviation sigma(phi) estimated on the basis of this model for the typical values of parameters significantly differs from the real values of sigma(phi).