AlGaAs/GaAs heterojunction bipolar transistors with heavily C-doped base layers grown by flow-rate modulation epitaxy

AlGaAs/GaAs heterojunction bipolar transistors are fabricated using carbon-doped p-type GaAs base regions grown for the first time by flow-rate modulation epitaxy. Because of the much smaller diffusion coefficient of carbon atoms in GaAs than that of beryllium and other p-type impurities, sharp impurity profiles are achieved. The heterojunction bipolar transistors exhibited high current gains up to 40 for a base layer width of 150 nm and base doping of 2.4×10¹⁹ cm^-3. The electron lifetime in heavily carbon-doped GaAs layers is considerably long, indicating favorable quality of heavily carbon-doped layers.