INVESTIGATION OF HIGH-CURRENT EFFECTS ON THE CURRENT GAIN OF ALXGA1-XAS/GAAS/GAAS ABRUPT HETEROJUNCTION BIPOLAR-TRANSISTORS

High-collector-current effects such as base pushout and base-collector space-charge-region thickness modulation, on the common-emitter d.c. current gain of AlxGa1-xAs/GaAs/GaAs abrupt heterojunction bipolar transistors is examined by including these effects in a recently developed thermionic-diffusion-field model. Current-gain falloff is predicted by the present model for transistors operating at high current densities (or at saturation mode), and comparison of the present model and measured data for an Al0.25Ga0.75As/GaAs/GaAs heterojunction bipolar transistor for digital and A/D applications is included.