The incorporation efficiency of carbon in GaAs using carbon tetrabromide (CBr4) was studied. A series of carbon-doped GaAs samples were grown at different CBr4 pressures and V/III ratios using solid source molecular beam epitaxy (SSMBE). The results showed a high carbon incorporation efficiency of similar to30% within the CBr4 pressure range up to 2 x 10(-7) Torr, which resulted in carbon doping concentration of up to 2 x 10(20) cm(-3). However, an increase in V/III ratio was found to reduce the carbon incorporation efficiency. Based on our experimental results, a kinetic model was developed to explain the effect of carbon incorporation in GaAs from CBr4 in SSMBE growth. The model incorporates the effects of different CBr4 decomposition rates on the As-covered and Ga-covered surface. (C) 2004 American Vacuum Society.