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

Abstract
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.