Strained-Silicon Heterojunction Bipolar Transistor

  1. Lookup NU author(s)
  2. Dr Stefan Persson
  3. Mouhsine Fjer
  4. Dr Enrique Escobedo-Cousin
  5. Dr Sarah Olsen
  6. Professor Anthony O'Neill
Author(s)Persson S, Fjer M, Escobedo-Cousin E, Olsen SH, Malm G, Wang YB, Hellstrom PE, Ostling M, O'Neill AG
Publication type Article
JournalIEEE Transactions on Electron Devices
ISSN (print)0018-9383
ISSN (electronic)1557-9646
Full text is available for this publication:
Experimental and modeling results are reported for high-performance strained-silicon heterojunction bipolar transistors (HBTs), comprising a tensile strained-Si emitter and a compressively strained $hbox{Si}_{0.7}hbox{Ge}_{0.3}$ base on top of a relaxed $hbox{Si}_{0.85}hbox{Ge}_{0.15}$ collector. By using a $hbox{Si}_{0.85}hbox{Ge}_{0.15}$ virtual substrate strain platform, it is possible to utilize a greater difference in energy band gaps between the base and the emitter without strain relaxation of the base layer. This leads to much higher gain, which can be traded off against lower base resistance. There is an improvement in the current gain $beta$ of 27$times$ over a conventional silicon bipolar transistor and 11$times$ over a conventional SiGe HBT, which were processed as reference devices. The gain improvement is largely attributed to the difference in energy band gap between the emitter and the base, but the conduction band offset between the base and the collector is also important for the collector current level.
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