High-Low Polysilicon-Emitter SiGe-Base Bipolar Transistors

Emmanuel F. Crabbé, James H. Comfort, Jack Y.C. Sun, Johannes M.C. Stork, John D. Cressler

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Self-aligned heterojunction bipolar transistors with a high-low emitter profile consisting of a heavily doped polysilicon contact on top of a thin epitaxial emitter cap have been fabricated. The low doping in the single-crystal emitter cap allows a very high dopant concentration in the base with low emitter-base reverse leakage and low emitter-base capacitance. The thin emitter cap is contacted by heavily doped polysilicon to reduce the emitter resistance, the base current, and the emitter charge storage. A trapezoidal germanium profile in the base ensures a small base transit time and adequate current gain despite high base doping. The performance potential of this structure was simulated and demonstrated experimentally in transistors with near-ideal characteristics, very small reverse emitter-base leakage current, 52-GHz peak fmax, and in unloaded ECL and NTL ring oscillators with, respectively, 24- and 19-ps gate delays.

Original languageEnglish
Pages (from-to)478-480
Number of pages3
JournalIEEE Electron Device Letters
Issue number10
StatePublished - Oct 1993


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