Prospects for 200 GHz on silicon with SiGe heterojunction bipolar transistors

Introducing some percent of germanium into the base of a silicon bipolar transistor does not necessarily improve device performance. Careful layer design and the choice of an appropriate fabrication technology are prerequisites for high speed SiGe HBTs that will lead to ft and/or f/sub max/-values above 200 GHz. This paper describes how the different HBT layers have to be designed in order to obtain a transistor with maximum ft or maximum f/sub max/. The different existing fabrication technologies are presented and compared. An overview of recently published SiGe HBT data is given.