Correlation between current leakage and structural properties of threading dislocations in GaN bulk single crystals grown using a Na-flux method.

This work investigated the electrical and microstructural properties of threading dislocations (TDs) in Na-flux-grown GaN bulk single crystals composed entirely of a c-plane growth sector (cGS). Several microscale Schottky-like contacts fabricated on TD-related etch pits and flat (0001) surfaces were analyzed via a combination of conductive atomic force microscopy, multi-photon excitation photoluminescence and transmission electron microscopy. Significant current leakage was observed in microscale facet growth sectors (μ-FGSs), having high local oxygen impurity concentrations, that had formed in the cGS. Higher leakage currents were found to be associated with bundled a type and a + c type TDs, whereas lower leakage currents were produced by single a type TDs. The leakage current evidently increased as the size of etch pits formed on the μ-FGSs increased. These observations establish a close correlation between current leakage and TD-induced strain fields that affect the distribution of point defects such as oxygen impurities around TDs. [ABSTRACT FROM AUTHOR]