Transit frequency of fast Si self-aligned bipolar transistors

The small-signal current gain β of fast Si self-aligned transistors is measured up to the transit frequency f_T using a 26.5-GHz microwave network analyzer system and special HF measuring probes. The influence of parasitic transistor elements such as the base-collector junction capacitance, the internal base resistance, and the peripheral transistor was confirmed in a real transistor at high frequencies by measurements on transistors with different emitter areas. The two-dimensional effects, which deviate from the expected one-pole frequency behavior of β, can be described by the extended transistor model, namely the intrinsic model and the peripheral model