Effects of barrier height inhomogeneities on the determination of the Richardson constant

Abstract

Extraction of the Richardson constant and Schottky barrier height from the current-voltage-temperature (I−V−T) characteristics of Schottky barrier contacts is greatly influenced by a variety of nonideal effects. Starting with an overview of the original Richardson plot and relevant modifications of the Richardson plot, this article discusses limitations of previous analytical approaches that attempt to account for the effects of barrier height inhomogeneities on the extracted Richardson constant. A temperature-driven fundamental change in the current conduction in an inhomogeneous Schottky diode from conduction dominated by low barrier height patches to conduction dominated by high barrier height regions is identified as a likely source for the bowing of the Richardson plot, and knowledge of which regime dominates the current transport is critical for accurate determination of the Richardson constant. A simple linear relation between the effective Richardson constant and effective barrier height is described, and this recently-reported linear relation provides a consistent method for estimating the Richardson constant of inhomogeneous Schottky diodes when transport is primarily through high barrier height regions. The method is applied to I−V−T characteristics of Au/Ni/n-GaN Schottky diodes measured from 320–440 K. A homogeneous Richardson constant of 29±6 A cm−2 K−2 is extracted using the proposed approach and is in very good agreement with the theoretical value of 26.4 A cm−2 K−2.