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Electrical investigation of V-defects in GaN using Kelvin probe and conductive atomic force microscopy

We report on the electrical characterization of V-defects in GaN-based heterostructures via Kelvin probe force microscopy (KPFM) and conductive atomic force microscopy (C-AFM). The KPFM measurements show for n- and p-doped GaN top layers an increase in the work function within the V-defects. Surprisingly, an increase in the current flow within the V-defects is found by C-AFM in case of the n-doped structure, while current flow into the V-defect is suppressed for the p-doped structure. For a consistent explanation of these results we suggest a model, which is based on an increase in the electron affinity of the {10−11}-surfaces within the V-defects as compared to the planar (0001)-surface.

Investigation of the electrical activity of V-defects in GaN using scanning force microscopy

We report on the characterization of V-defects in GaN-based heterostructures via scanning force microscopy techniques. The diameter and density of the V-defects are found to strongly depend on growth thickness and temperature of the top layer, respectively, while no correlation between the V-defect formation and the type of doping could be identified. Kelvin probe force microscopy measurements revealed for both, n- and p-doped GaN top layers, a decrease of the Kelvin voltage within the V-defects, which indicates an enhanced work function of the facets of the V-defects with respect to the planar surface. Surprisingly, an increase of the current flow within the V-defects is found by conductive atomic force microscopy in case of the n-doped top layer, while current flow into the V-defect is suppressed for the p-doped top layer. For a consistent explanation of these results we suggest a model, which is based on an enhanced electron affinity of the {10-11}-surfaces within the V-defects as compared to the planar (0001)-surface.