Dislocation generation from scratches induced on a bare GaN wafer during the wafer-fabrication process was investigated via multi-photon excitation photoluminescence (MPPL). The scratch was detected as a faint dark contrast by MPPL but had no accompanying dark dislocation loops that expanded on both sides of the scratch in the GaN wafer. The acceptable quality level for the wafer-fabrication process was determined. Dislocations generated from the scratch elongated to the surface with the repetition of the dislocation reaction. The repetition of the dislocation reaction results in the variation of dislocation types ( a , c , and c +  a ). The dislocation structures formed after the dislocation reaction appeared to both decrease as well as increase the dislocation energy. The reactions that appeared to increase the dislocation energy could primarily be attributed to the reaction of threading and half-loop dislocations.

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