The growth and characteristics of ultrahigh carbon-doped p-type InGaAs lattice matched to InP by gas source molecular beam epitaxy (GSMBE) using carbon tetrabromide (CBr4) as a doping source was investigated. The effects of growth temperature, group V supply pressure and CBr4 supply pressure on the composition, hole mobility and concentration of carbon-doped InGaAs were studied. The dependence of hydrogen passivation effect on different AsH3 supply pressure and different growth temperature were researched. Ultrahigh net hole concentration and room-temperature mobility of 1 x 10(20) cm(-3) and 45 cm(2)/V s, respectively, were achieved without any postgrowth annealing. Mobility of the ultrahigh carbon-doped InGaAs using CBr4 compared favorably to those of CBE grown carbon-doped InGaAs using CBr4 and molecular beam epitaxy grown beryllium (Be)-doped InGaAs grown at low temperature. The highly carbon-doped InGaAs layers grown by GSMBE using CBr4 as a doping source were used for the growth of high performance, highly carbon-doped base InP/InGaAs heterojunction bipolar transistor epitaxial layer structures. (c) 2006 Elsevier B.V. All rights reserved.