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(HBTEM).AFM images show that the islands appear in the GaN buffer layer after annealing at high temperature.Cross-sectional HBTEM micrographs of the buffer region of these samples indicate that there are bunched steps on 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 Him on a terrace between steps have the same crystal orientation.An amorphous-like layer,about 3nm thick,can also be observed between the GaN buffer layer and the Si substrate.