A study on the classification of threading dislocations in GaN substrate by spot size using X-ray topography high-resolution image

We studied the classification of threading dislocations in an ammonothermal GaN substrate by analyzing the spot size in dislocation images obtained via synchrotron back-reflection X-ray topography. The spot size reflects the lattice distortion or strain surrounding the dislocations, enabling us to categorize the dislocation types based on their respective spot sizes. To achieve this, we employed both a high-quality X-ray camera and a high monochromatic X-ray. Consequently, we classified the dislocations based on spot size in X-ray topography images using the 0008-reflection plane and experimentally determined that the small, middle, and large spots correspond to edge dislocations, mixed dislocations with b = na + 1c (n = 1, 2), and mixed dislocations with Burgers vectors with b = na + 2c(n = 1, 2), respectively. This method is promising for the non-destructive classification of dislocations across an entire surface in a short time.