Behavior of Threading Dislocations from GaN Substrate to Epitaxial Layer

Threading dislocations (TDs) in the GaN substrate and homoepitaxial layer are nondestructively evaluated using X-ray topography (XRT), Raman spectroscopy, and multiphoton photoluminescence (MPPL) imaging. When the XRT and Raman mapping images are compared, TDs in the GaN substrate are identified as threading edge dislocations (TEDs), threading mixed dislocations (TMDs), and threading screw dislocations (TSDs). TDs are observed to propagate from the GaN substrate to the epitaxial layer. From MPPL imaging, the TEDs are found to be inclined in the [11 over bar 00] direction, which is at 90 degrees from the Burgers vector. The TMD studied in detail is found to be inclined in the [1 over bar 21 over bar 0] direction, which is parallel to the Burgers vector. The feasibility of identifying TDs via analysis of the inclined direction of the dislocations in the GaN epitaxial layer is suggested.