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As device scaling for higher performance bipolar transistors continues, the operation current density increases as well. To investigate the reliability impact of the increased operation current density on Si-based bipolar transistors, an accelerated-current wafer-level stress was conducted on 120-GHz SiGe heterojunction bipolar transistors (HBTs), with stress current density up to as high as JC=34 mA/μm2. With a novel projection technique based on accelerated-current stress, a current gain shift of less than ∼15% after 106 h of operation is predicted at T=140°C. Degradation mechanisms for the observed dc parameter shifts are discussed for various VBE regions, and the separation of the current stress effect from the self-heating effect is made based on thermal resistance of the devices. Module-level stress results are shown to be consistent with wafer-level stress results. The results obtained in this work indicate that the high-speed SiGe HBTs employed for the stress are highly reliable for long-term operation at high operation current density.