EPITAXY OF AL FILMS ON GAN STUDIED BY REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION AND ATOMIC-FORCE MICROSCOPY

Epitaxy of Al films deposited on GaN has been studied using reflection high-energy electron diffraction (RHEED), atomic force microscopy (AF M), x-ray diffraction, and ion channeling techniques. Al (111) films h ave been found to grow epitaxially on GaN (0001) surfaces with Al <[2( 11)over bar]>parallel to GaN<[2(11)over bar 0]>. For growth at 15 and 150 degrees C with a deposition rate of 0.26 Angstrom/s, the epitaxial quality of the film was poor initially, as evidenced by the observati on of diffuse RHEED patterns. After a few monolayers, a sharp and stre aky RHEED pattern develops and is maintained during subsequent deposit ion, indicating an improvement in epitaxial quality with a two-dimensi onal growth mode. AFM studies indicate that the initial GaN surface qu ality is a significant factor in achieving epitaxial growth, and that the size of Al epitaxial islands increases substantially for higher gr owth temperatures. X-ray diffraction and ion channeling results confir m the epitaxial nature of the Al films in spite of a significant latti ce mismatch of 10.2%. (C) 1997 American Institute of Physics.