Heterojunction bipolar transistor using pseudomorphic GaInAs for the base

We report on replacing the GaAs base in the AlGaAs/GaAs heterojunction bipolar transistor with pseudomorphic GaInAs. Base regions consisting of uniform Ga0.95In0.05As and graded Ga1−yInyAs (y=0.0–0.05) are compared to base regions consisting of GaAs. The highest dc common emitter current gain is obtained with the graded Ga1−yInyAs base.