Inhomogeneous spatial distribution of reverse bias leakage in GaN Schottky diodes

The reverse bias leakage current in macroscopic GaN Schottky diodes is found to be insensitive to barrier height. Using a scanning current-voltage microscope, we show that the reverse bias current occurs at small isolated regions, while most of the sample is insulating. By comparing the current maps to topographic images and transmission electron microscopy results, we conclude that reverse bias leakage occurs primarily at dislocations with a screw component. Furthermore, for a fixed dislocation density, the V/III ratio during the molecular beam epitaxial growth strongly affects reverse leakage, indicating complex dislocation electrical behavior that is sensitive to the local structural and/or chemical changes.