Carbon doping of InxGa1−xAs grown on GaAs and InP substrates by low‐pressure metalorganic chemical vapor deposition (LP‐MOCVD) using CCl4 has been investigated for In mole fractions as high as x=0.53. P‐type conduction was obtained over the entire composition range studied, with hole concentrations above 1×1020 cm−3 for x<0.12, and as high as 1×1019 cm−3 for In0.53Ga0.47As lattice‐matched to InP. These high carbon concentrations were achieved by employing very low V/III ratios and low growth temperatures. The alloy composition was found to be dependent on several growth parameters, including CCl4 partial pressure, V/III ratio, and growth temperature. This may be due to surface reactions (etching) involving chlorine‐containing compounds during growth. Samples grown at low temperature (∼500 °C) and lattice matched to InP exhibited an increase in hole concentration upon post‐growth annealing.