RF power characteristics of SiGe HBTs at cryogenic temperatures

Meng Wei Hsieh, Yue Ming Hsin, Kung Hao Liang, Yi Jen Chan, Denny Tang

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


This paper investigates the temperature dependence (from 77 to 300 K) of dc, ac, and power characteristics for n-p-n SiGe heterojunction bipolar transistors (HBTs) with and without selectively implanted collector (SIC). In SiGe HBTs without SIC, the valance band discontinuity at the base-collector heterojunction induces a parasitic conduction band barrier while biasing at saturation region and high current operation at cryogenic temperatures. This parasitic conduction band barrier significantly reduces the current gain and cutoff frequency. For transistors biased with fixed collector current, the measured output power, power-added efficiency, and linearity at 2.4 GHz decrease significantly with decreasing operation temperatures. The temperature dependence of output power characteristic is analyzed by Kirk effect, current gain, and cutoff frequency at different temperatures. The parasitic conduction band barrier in SiGe HBTs with SIC is negligible, and thus the device achieves better power performance at cryogenic temperatures compared with that in SiGe HBT without SIC.

Original languageEnglish
Pages (from-to)1452-1458
Number of pages7
JournalIEEE Transactions on Electron Devices
Issue number6
StatePublished - Jun 2006


  • Conduction band barrier
  • Cryogenic temperatures
  • Power capability


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