Inhomogeneous spatial distribution of reverse bias leakage in GaN Schottkydiodes

The reverse bias leakage current in macroscopic GaN Schottky diodes is foun d to be insensitive to barrier height. Using a scanning current-voltage mic roscope, we show that the reverse bias current occurs at small isolated reg ions, while most of the sample is insulating. By comparing the current maps to topographic images and transmission electron microscopy results, we con clude that reverse bias leakage occurs primarily at dislocations with a scr ew component. Furthermore, for a fixed dislocation density, the V/III ratio during the molecular beam epitaxial growth strongly affects reverse leakag e, indicating complex dislocation electrical behavior that is sensitive to the local structural and/or chemical changes. (C) 2001 American Institute o f Physics.