This paper reports the surface morphology of carbon-doped GaAs (GaAs:C) samples grown by solid source molecular beam epitaxy (SSMBE) using carbon tetrabromide (CBR4) as p-dopant source. Sample characterization was carried out using Hall effect, X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements. The results show that samples grown at 650degreesC contain dicarbon defects and the surface morphology is rough. Further experiments on two different sets of GaAs:C samples have shown the absence of bromine-related surface roughening reactions during GaAs:C growth, and the presence of dicarbon defects contribute to the rough surface morphology. It is suggested that the presence of dicarbon defects disrupt the two-dimensional (2-D) step flow growth mode and promote three-dimensional (3-D) growth of GaAs:C through a step bunching mechanism. (C) 2003 Elsevier B.V. All rights reserved.