Base current transient behavior in polyimide-passivated InP/InGaAs heterojunction bipolar transistors

We have investigated a transient effect in the base current in polyimide passivated InP/InGaAs heterojunction bipolar transistors (HBTs) and its influence on the device characteristics. The trapping and detrapping of static charge in the polyimide at the polyimide/semiconductor interface is found to be the root cause of the base current transient. We have also found that the transient effect can be suppressed by post-process high-dose UV exposure.