The Burton-Cabrera-Frank (BCF) theory has been applied to metalorganic vapor-phase epitaxy (MOVPE) of N-polar (0001) GaN. Owing to the hydrogen-rich atmosphere during MOVPE, surface N atoms of the N-polar (000-1) surface are mostly covered with H atoms. Extremely small coverage of the Ga adatoms competing with the H adatoms on the terraces can be calculated using the Langmuir adsorption isotherm. The equilibrium coverage of the Ga adatoms at steps and the equilibrium pressure of the NH3 gas at step kinks can be calculated from the conditions of Gibbs energy balance between the sources (Ga adatom and NH3 gas molecule) and the products (GaN and 3/2 H2 gas molecules) and of speed balance between Ga and N incorporation into the step kinks. Growth rates of GaN on vicinal surfaces and hexagonal spiral pyramids has been calculated as a function of the trimethylgallium flow rate and compared with experimental results.
