Gallium nitride (GaN) layers have been epitaxially grown by the metalorganic vapor-phase epitaxy technique using trimethylgallium (TMG) and tertiarybutylhydrazine (TBHy) as the reactants at temperatures ranging from 923 to 958 K and a low pressure of 10 Torr. A film growth model based on the Langmuir-Hinshelwood-type reaction is established to describe the growth behavior of GaN from TMG and TBHy. By model fitting, the experimental growth rate data, the adsorption equilibrium constant of TBHy is found to be 1/7 that of TMG at the above temperature range, indicating the possibility to obtain stoichiometric GaN films at quite small V/III precursor feed ratios. Additionally, a comparison of the carbon incorporation when dimethylhydrazine (DMHy) is used as the nitrogen source is also made. The result shows that the films formed using TBHy have much less carbon content than those formed using DMHy. The beta-hydride elimination in the t-butyl ligand of TBHy occurs to form a stable hydrocarbon species, thus taking away the carbon contaminants might explain this phenomenon. (C) 2003 Elsevier Science B.V. All rights reserved.