The structural evolution of GaN films during the initial growth process of
metalorganic chemical vapor deposition (MOCVD) - low temperature nucleation
layer growth, annealing, and high temperature epitaxial growth - was inves
tigated in a synchrotron x-ray scattering experiment. The nucleation layer
grown at 560 degreesC that was predominantly cubic GaN consisted of tensile
-strained aligned domains and relaxed misaligned domains. The hexagonal GaN
, transformed from the cubic GaN during annealing to 1100 degreesC, showed
disordered stacking. The atomic layer spacing decreased as the fraction of
the hexagonal domains increased. Subsequent growth of epitaxial GaN at 1100
degreesC resulted in the Formation of ordered hexagonal GaN domains with r
ather broad mosaicity.