Structural evolution of GaN during initial stage MOCVD growth

Abstract

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 investigated 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 rather broad mosaicity.