Kinetic roughening during gas-source molecular-beam epitaxy of gallium nitride

We have used ex situ atomic force microscopy (AFM) to investigate the evolution of GaN(0 0 0 1) surface roughness as a function of growth time. Samples were grown on Si(1 1 1) substrates by molecular-beam epitaxy (MBE) using ammonia as a nitrogen source. Above thickness of 0.6–0.7 mm, further growth apparently leads to kinetic roughening. The kinetic origin of the roughness developed during the MBE growth is first evidenced by the drastic decrease of the surface roughness obtained by hightemperature post-growth annealing. This is confirmed by a detailed study of the morphological pattern evolution as function of the thickness (t). The surface width (w) is found to scale as tb with the dynamic exponent b 0:3. # 2004 Elsevier B.V. All rights reserved.