Surface potential imaging and characterizations of a GaN p-n junction with Kelvin probe force microscopy

We applied Kelvin probe force microscopy (KPFM) to characterize the p-n junction grown on hydride vapor-phase epitaxy GaN wafers with three different doses of the p-type dopant Mg. The distributions of the contact potential difference (CPD) were visualized to observe the abrupt changes in the CPD across the p-n junction. Based on this result, we attempted to evaluate the electrostatic potential distributions across the GaN p-n junction, which consequently provide the dopant concentrations in the p-type region (NA) and unintentionally doped regions (NUID). The obtained values of NA in this study were two orders of magnitude smaller than doped Mg concentrations, while those of NUID were consistent with the results of secondary ion mass spectroscopy. We demonstrate the potential of KPFM in the evaluation of GaN p-n junctions.