Highly-reliable and reproducible InGaAs/InP double heterojunction bipolar transistor utilizing all-wet etching process for triple mesa formation

The authors have succeeded in making a robust fabrication process applied to InP-based double heterojunction bipolar transistors. The process, featuring all-wet etching method for formation of triple-mesa structure, has shown markedly high reproducibility and reliability. The variation of the current gain has been 4.6% through 130 wafers, and the mean time to failure at the junction temperature of 100°C has been longer than 4 × 10⁶ hours, whose criterion is a 5% change in current gain. These excellent results show that our structure of DHBT, which has an InP passivation layer on the surface of the base layer, and our all-wet mesa formation process, are sufficient to be applied to the manufacturing of integrated circuits.