Evaluation of dislocations under the electrodes of GaN pn diodes by X-ray topography

Abstract

We have successfully obtained the clear images of the dislocation mapping even under the electrodes of the GaN vertical pn diodes by reflection X-ray topography using monochromatic synchrotron radiation (SPring-8, BL16B2 & BL20B2). This is a powerful analysis because of the non-destructive and rapid tool unlike the etch-pit method and TEM (transmission electron microscopy). This allows us to directly study the relationship between the dislocation and the leakage current. Applying this method to vertical pn diodes on Na-flux GaN substrates, we found that leakage current per dislocation is of the order of 10 pA. This analysis has a potential to reveal the killer dislocation structure.