Anisotropic Step-Flow Growth and Island Growth of GaN(0001) by Molecular Beam Epitaxy

Anisotropic growth is observed for GaN(0001) during molecular beam epitaxy for both the step-flow growth mode and two-dimensional (2D) nucleation growth mode. Using scanning tunneling microscopy, we find that in the step-flow growth mode, growth anisotropy strongly influences the shape of terrace edges, making them strikingly different between hexagonal and cubic films. In the 2D nucleation growth mode, anisotropic growth results in triangularly shaped islands. The importance of understanding growth anisotropy to achieve better grown GaN films is discussed.