GaN Layers on Si (111) from Nanocolumns to Nanorods by Plasma-Assisted Molecular Beam Epitaxy

In this report, the characterization of GaN layers grown on p-type Si (111) substrate by plasma-assisted molecular beam epitaxy was investigated. For different growth temperatures (750 degrees C, 800 degrees C and 850 degrees C) and N/Ga flux ratios (0.26, 0.46 and 0.92), we can find the GaN layers transition from nanocolumns to nanorods structures. During the epitaxy of GaN, nanocolumns in the thin films with poor crystal quality were obtained for the growth parameters of low substrate temperature or Ga-rich condition. However, the growth at high substrate temperature or N-rich condition formed GaN nanorods structure, and was beneficial to the crystallization of GaN layers with preferential orientation (0001). In the end, the possible growth mechanism of GaN nanocolumns and nanorods was discussed in the letter.