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 (N-A) and unintentionally doped regions (N-UID). The obtained values of N-A in this study were two orders of magnitude smaller than doped Mg concentrations, while those of N-UID were consistent with the results of secondary ion mass spectroscopy. We demonstrate the potential of KPFM in the evaluation of GaN p-n junctions.