Three-dimensional imaging of threading dislocations in GaN using stimulated Raman scattering microscopy

We present stimulated Raman scattering (SRS) microscopy for three-dimensional (3D) imaging of threading dislocations (TDs) in gallium nitride (GaN) substrates. SRS microscopy enhances Raman signals with two picosecond pulses, shortening the pixel dwell time by a few orders of magnitude compared to spontaneous Raman microscopy. Compatibility of SRS microscopy with multiphoton photoluminescence (MPPL) allows for simultaneous SRS and MPPL imaging. This multimodal approach enables accurate tracking of TD positions, fusions, and interactions while detecting the edge component of the Burgers vector. Furthermore, SRS is insensitive to the screw component, while MPPL reacts to all TD types. This difference between SRS and MPPL facilitates the identification of screw-type TDs, which are particularly critical ones since they cause leakage current in p-n junctions. Our multimodal imaging technique for comprehensive 3D characterization of TDs in GaN will be useful to improve crystal growth methods and device performance.