Numerical simulation of GaAs/GaAlAs heterojunction bipolar transistors

A numerical analysis program for the 1-dimensional simulation of GaAs/GaAlAs heterojunction bipolar transistors is described. Calculations for a representative transistor structure indicate that a cutoff frequency, ft, of 100 GHz is obtainable. To attain such a high value, the transistor design incorporated a graded-bandgap base region and relatively high emitter doping (5 × 10¹⁷cm^-3), and the device was operated at high current density (5 × 10⁴A/cm²). Transient electron velocity overshoot effects were also included.