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-b urn-in Al-GaAs/GaAs heterojunction bipolar transistor (HBT) are studie d. It is shown experimentally that the burn-in test gives rise to a la rger I(B) but does not alter I(C) notably. An empirical model which ca n explain such trends is also developed. The model suggests that the i ncreased 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 s urface and base bulk recombination currents. Such occurrences can be a ttributed to the recombination/thermal enhanced diffusion of defects f rom GaAs surface and bulk to dislocations near the hetero-interface.