Recombination current reduction in AlGaAs/GaAs heterojunction bipolar transistors with polyimide deposition

Abstract

N-p-n AlGaAs/GaAs heterojunction bipolar transistors of various emitter-mesa diameters have been fabricated to examine the effects on the recombination current with polyimide deposition. The recombination current in these devices (when the ideality factor is close to 2) was proportional to the device perimeter before and after polyimide deposition. This suggests that the dominant component of the recombination current in these devices is the perimeter recombination current. A simple model was developed which allowed the contribution from the perimeter and bulk recombination currents to be calculated. The common-emitter d.c. current gains of these devices increased correspondingly as recombination current decreased due to the polyimide deposition.