InP/GaInAsSb DHBT evolution in the THz era

The InP-GaAsSb material system is an alternative to InP-GaInAs for the realization of high-speed double heterostructure bipolar transistors (DHBTs) on InP substrates. This paper will review the evolution of InP/GaAsSb DHBTs over the last two decades, and will identify remaining challenges and opportunities. The characteristics of InP/GaAsSb DHBTs will be differentiated from those of the InP/GaInAs variant to clarify the technological trade-offs facing users. The state-of-the-art with both GaAsSb and GaInAsSb bases will be examined and prospects for THz devices given considering maximum oscillation frequencies exceeding 1.1 THz have already been obtained in our laboratory. Difficulties in RF performance assessment will be discussed and the approaches taken at ETH-Zürich discussed.