We present real-time surface x-ray scattering measurements during homoepita
xial growth of GaN by metal-organic chemical vapor deposition. We observed
intensity oscillations corresponding to the completion of each monolayer du
ring layer-by-layer growth. The growth rate was found to be temperature ind
ependent and Ga-transport limited. Transitions between step-flow, layer-by-
layer, and three-dimensional growth modes were determined as a function of
temperature and growth rate. (C) 1999 American Institute of Physics. [S0003
-6951(99)01622-8].