Mapping of n‐GaN Schottky Contacts With Wavy Surface Morphology Using Scanning Internal Photoemission Microscopy

Abstract

We characterized the effects of surface morphology on the electrical properties of n‐GaN drift‐layers by using scanning internal photoemission microscopy (SIPM). We grew 12‐μm‐thick low carrier concentration (approximately 1 × 1016 cm−3) n‐GaN layers with both flat and wavy surface morphologies on freestanding GaN substrates by metal organic chemical vapor deposition. In the SIPM results, the samples with flat surfaces exhibited a uniform photocurrent distribution independently of the carrier concentration. In contrast, wavy patterns in the photocurrent maps were the same as the surface morphology for samples with low carrier concentration. These results indicate that the amount of C incorporated during the growth was affected by the off‐angle of the GaN surface, and the carrier compensation by C atoms was changed. We demonstrated that SIPM is a powerful tool for nondestructively visualizing the inhomogeneity of the carrier compensation over the wafers.