Carbon doping in III–V compounds has generated much attention because of applications in high temperature and high current devices. We present results using a novel electron beam carbon source for doping GaAs and GaSb. The source construction allows normal effusion cell geometry and utilizes electron bombardment for evaporation from a carbon rod. Mass spectrometer data showed the carbon flux contained C1, C2, and C3species. For GaAs, controllable hole doping densities between 3×1015cm−3and 5×1019cm−3were obtained. For GaSb, carbon doping resulted inP‐type material with hole densities ranging from the background level of 2×1016to 3×1020cm−3for specular film morphology. Hole mobility values for GaAs and GaSb are comparable to published data.