Abstract
The kinetics of the heteroepitaxial film growth of 
on sapphire by chemical vapor deposition was investigated under a variety of experimental conditions. The growth rate was observed to be linear with time for all conditions studied and was found to be significantly influenced by the following factors: composition of the reactants in the vapor, temperature in the reaction zone, substrate orientation, and dopant concentration. The Gibbs free energy change for the main deposition reaction was evaluated as a function of temperature and reactant composition using available thermochemical data and compared with the observed deposition rate. An apparent discrepancy between predicted and observed deposition rate was attributed to local differences in 
composition due to decomposition and/or to the uncertainty in available thermochemical data. Significant observations are reported concerning the decomposition kinetics of 
in different growth ambients.