Abstract
Atom probe tomography (APT) provides the three-dimensional imaging of materials and their compositional information at atomic-scale resolution. However, various factors such as the limited volume and/or the imperfect detection efficiency sometimes make it difficult to fully understand a material only by APT. The combination of APT with scanning transmission electron microscopy (STEM) in GaN-based systems allows more reliable information of complex problems such as magnesium (Mg) segregations in extended defects or indium (In) fluctuations in multiple quantum wells. The combined analyses have revealed that Mg atoms in GaN are likely to be segregated in polarity inversion domains formed through post-implantation annealing. This combinational approach also provided a direct evidence of Mg atoms diffusing along threading dislocations in the p-n junction of GaN; such information is useful to understand the mechanism of leakage current in the junction. Combined use of APT and STEM also revealed the existence of In clusters and compositional fluctuations in InGaN/GaN multiple quantum wells, which can be used to understand carrier localization in these system. This chapter reviews the remarkable achievements obtained via combined APT and STEM analyses in GaN based materials and devices, and discusses the future outlook.
Published Version
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