BASE AND COLLECTOR CURRENTS OF PRE-BURN-IN AND POST-BURN-IN ALGAAS/GAAS HETEROJUNCTION BIPOLAR-TRANSISTORS

The base and collector currents (I(B) and I(C)) of the pre- and post-burn-in Al-GaAs/GaAs heterojunction bipolar transistor (HBT) are studied. It is shown experimentally that the burn-in test gives rise to a larger I(B) but does not alter I(C) notably. An empirical model which can explain such trends is also developed. The model suggests that the increased I(B) in the post-burn-in HBT results from an increase in the space-charge region recombination current and a decrease in both the surface and base bulk recombination currents. Such occurrences can be attributed to the recombination/thermal enhanced diffusion of defects from GaAs surface and bulk to dislocations near the hetero-interface.