Carbon doping of epitaxial InSb films grown by gas-source molecular beam epitaxy was studied using carbon tetrabromide as the carbon dopant source. Carbon was found to be ap-type dopant in InSb, yielding the highest as-grown acceptor concentrations to date, up to mid1020 cm−3as deposited. Room temperature mobilities ranged from 35 to90 cm2/V sdepending upon doping level. The hole concentration was found to be relatively insensitive to growth temperature between 325 and 400 °C. Higher growth temperatures required higher Sb fluxes in order to maintain a constant hole concentration. Hole concentration increased linearly with increasingCBr4up to5×1020 cm−3.Further increase in the dopant flow reduced the hole concentration and mobility and produced polycrystalline material. ©1998 American Institute of Physics.