The effect of atomic bond structure at the deposition surface on the crystallographic orientation dependence of carbon doping in GaAs was studied. Carbon doping into GaAs epilayers was performed by atmospheric pressure metalorganic chemical vapor deposition using extrinsic carbon sources of carbon tetrachloride (CCl4) and carbon tetrabromide (CBr4). Epitaxial growths were done on the exact (100) and four different misoriented GaAs substrates with orientations of (511)A, (311)A, (211)A, and (111)A. The electrical properties were measured by van der Pauw Hall analysis at room temperature. Electrically active concentrations in excess of 1×1019 cm-3 were obtained so that CCl4 and CBr4 were demonstrated as efficient p-type dopant sources for carbon doping into GaAs. The dependence of hole concentration on the offset angle of CCl4-doped and CBr4-doped GaAs shows the same tendency, whereas the trend of carbon doping from intrinsic carbon doping technique is different from our results. In particular, the hole concentration on the (100) surface is higher than that on the (111)A surface in the cases of CCl4 and CBr4. The result is opposite to that of the intrinsic doping case. A model based on the atomic bond structure of an adsorption site of carbon-containing species is proposed to explain the difference.