Understanding formation and distribution of defects in GaN substrates and device layers is needed to improve device performance in RF- and power-electronics. Here we utilize conductive atomic force microscopy (c-AFM) for studying defect-related leakage paths in an unintentionally doped GaN film formed by nanowire reformation. A nanoscopic Schottky contact is formed between the c-AFM probe and the GaN surface, which, under reverse bias conditions, reveals local leakage-currents at the positions of the nanowires. Cathodoluminescence shows these areas to be dominated by yellow band luminescence, in contrast to the surrounding GaN matrix, which mainly shows near-bandgap luminescence. These results are attributed to a high density of native and residual defects, confined to the nanowires. In addition, we use anodic oxidation to map defect-related conductive paths through locally induced growth of gallium oxide. The oxide yield, which is known to depend on the local electric field strength between the AFM tip and the sample, correlates well with the level of reverse-bias leakage current. Local irregularities in oxide height reveal extended oxidation, attributed to defect-related deep level states. This is confirmed by controlled dissolution of the oxide in NaOH, showing that a deeper oxide film is grown over areas where defect-related conductive paths are formed. Finally, we demonstrate how this approach can be used as a quick and easy diagnostic tool for evaluating the influence of specific growth conditions and process steps on defect-induced leakage current levels and defect distribution in GaN structures, demonstrating its potential for accelerated test of leakage degradation at critical positions in GaN based devices.

中文翻译：

---

重整的GaN纳米线的局部缺陷增强阳极氧化

需要了解GaN衬底和器件层中缺陷的形成和分布，以改善RF和功率电子学中的器件性能。在这里，我们利用导电原子力显微镜（c-AFM）研究由纳米线重整形成的无意掺杂的GaN膜中与缺陷相关的泄漏路径。在c-AFM探针和GaN表面之间形成了纳米级的肖特基接触，在反向偏置条件下，该纳米级的肖特基接触揭示了纳米线位置处的局部漏电流。与周围的GaN基体（主要显示近带隙的发光体）相比，阴极发光显示这些区域以黄带发光体为主。这些结果归因于局限于纳米线的高密度的自然缺陷和残余缺陷。此外，我们使用阳极氧化通过局部诱导的氧化镓生长来映射与缺陷相关的导电路径。已知氧化物的产率取决于AFM尖端和样品之间的局部电场强度，它与反向偏置泄漏电流的水平密切相关。氧化物高度的局部不规则性揭示了扩展的氧化，这归因于与缺陷相关的深能级状态。这可以通过氧化物在NaOH中的受控溶解得到证实，表明在形成与缺陷相关的导电路径的区域上生长了更深的氧化膜。最后，我们演示了如何将该方法用作快速简便的诊断工具，以评估特定生长条件和工艺步骤对缺陷诱导的泄漏电流水平和GaN结构中缺陷分布的影响，