Inhomogeneity-mediated systematic reduction of the Schottky barrier in a Au/GaN nanorod film interface

Abstract

Self-aligned GaN nanorods of various densities are grown on an r-plane Al2O3 substrate with Stranski–Krastanov or layer-plus-island growth conditions by using a plasma-assisted molecular beam epitaxy system. These conditions result in the formation of a GaN nanorod matrix on an epitaxial GaN thin film. The orientation of the nanorods was found to be at an inclination of ∼60° from the substrate. As expected, the GaN thin film grows along the [11–20] direction, but interestingly the nanorods have a preferential growth direction along the [0002] axis. The overall structure mimics the Gaussian distribution of Schottky barriers at the metal–semiconductor interface. The GaN nanorod/thin-film matrix systematically causes the well-known Au/GaN Schottky metal–semiconductor interface to display an Ohmic type of behavior. A systematic reduction of the Schottky barrier is observed with an increase in the GaN nanorod density (from 5 to 65 nanorods micron−2). The overall configuration provides a tunable Gaussian distribution of Schottky barriers with nanorod density, which could be extremely useful for replacing conventional multi-level electrode stacking techniques.