The influence of subhydride species generated in a low‐pressure Ta‐based AsH3 cracker on the degree of H passivation of C acceptors in heavily doped (p⩾3×1019 cm−3) In0.53Ga0.47As grown by gas source and metalorganic molecular beam epitaxy has been studied. A strong correlation has been observed between the relative abundance of AsH3, AsH, and H in quadrupole mass spectra and the degree of passivation. Enhanced effects were observed at reduced growth temperatures. Design of experiments techniques have been used to study the influence of hydride cracker temperature, substrate temperature, H2 pumping speed, group III sources, AsH3 flow rate and the second order interactions on the H passivation of C acceptors. The substrate temperature, hydride cracking temperature, and H2 pumping speed, were determined to have the dominant effects, while second order interactions were dominated by substrate temperature, H2 pumping speed, and AsH3 flow rate interactions with the hydride cracking temperature. Optimized parameters were determined that permit the growth of essentially unpassivated (⩽10%) C‐doped In0.53Ga0.47As with net hole concentrations as high as p=8×1019 cm−3 by both gas source and metalorganic molecular beam epitaxy techniques. © 1996 American Institute of Physics.