Scanning reflection electron microscopy study of surface defects in GaN films formed by epitaxial lateral overgrowth

We have used scanning reflection electron microscopy (SREM) to detect surfa ce defects in GaN films formed by facet-initiated epitaxial lateral overgro wth. SREM revealed individual threading dislocations and single atomic step s on the GaN surface, and provided images of crystallographic tilting near the surfaces. We found that one of the two tilted GaN crystals in the overg rown areas became dominant and that the surface changed to a single domain after 50-mu m-thick GaN deposition. Our SREM results also showed that the d eposition of thick (over 100 mu m) GaN films significantly improves the cry stallographic structures of the overgrown regions, and reduces the threadin g dislocations in the GaN films. (C) 2000 American Institute of Physics. [S 0003-6951(00)00938-4].