InP DHBT Analytical Modeling: Toward THz Transistors

InP double heterojunction bipolar transistors (InP DHBTs) are one of the key technologies considered for terahertz (THz) applications. The improvement of their frequency performance is challenging and strongly dependent on various parameters (manufacturing process, geometry, and epitaxial structure). In this article, a novel method is developed to take into account these parameters and predict the frequency performance of the technology. This approach consists of rebuilding the S-parameter matrix of the small-signal model. Elements of the small signal model are identified, and their assessment is described in detail. Once calibrated with the present state-of-the-art device features, the model shows a good agreement with the measurements. Based on this result, analysis of the emitter and base technological features are performed along with optimizations of the vertical structure. Finally, the necessary optimizations for developing a THz transistor are detailed. This works provides guidelines for technological improvement and opens the way for designing transistors operating at frequencies above a THz.