Growth of thick GaN films on RF sputtered AlN buffer layer by hydride vapor phase epitaxy

High crystalline quality thick GaN films were grown by vapor phase epitaxy using GaCl3 and NH3. The growth rate was in the range of 10 similar to 15 mu m/h. GaN films grown at higher temperatures (960 similar to 1020 degrees C) were single crystalline with smooth surface morphologies. No chlorine impurity was incorporated in these films during growth. The best crystalline quality and surface morphology of grown films was achieved by sputtering a thin AIN buffer layer, prior to growth. According to reflection high energy electron diffraction and atomic force microscopy measurements, as-sputtered AIN buffer layer was amorphous with root means square roughness of 0.395 nm and then crystallized during the GaN growth. This improved the GaN growth due to more uniform distribution of GaN nucleation. Rutherford backscattering channeling experiments produced the lowest value from the GaN film grown on a-AL(2)O(3) with a 500 Angstrom AIN buffer layer at 1020 degrees C.