Microstructures of GaN buffer layers grown on Si(111) using rapic thermal process low-pressure metalorganic chemical vapor deposition

Microstructures of GaN buffer layers grown on Si (111) substrates using rapid thermal process low-pressure metalorganic chemical vapor deposition are investigated by an atomic force microscope (AFM) and a high-resolution transmission electron microscope (HRTEM). AFM images show that the islands appear in the GaN buffer lapel after annealing at high temperature. Cross-sectional HRTEM micrographs of the buffer region of these samples indicate that there are bunched steps an the surface of the Si substrate and a lot of domains in GaN misorienting each other with small angles. The boundaries of those domains locate near the bunched steps, and the regions of the film on a terrace between steps have the same crystal orientation. An amorphous-like layer, about 3 nm thick, can also be observed between the GaN buffer layer and the Si substrate.