Low-frequency noise properties of SiGe heterojunction bipolar transistors

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

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


In this study, we investigated the low-frequency noise in SiGe heterojunction bipolar transistors (HBTs) with and without a selectively implanted collector (SIC). By comparing the magnitude of 1// noise, collector current, and current gains of the SiGe HBTs with and without SIC, we show that the impurities at the collector produced by the incomplete activation of the implanted ions cause an increase in the collector current 1/f noise spectrum. Thus, SiGe HBT with SIC exhibits higher collector noise current spectra due to the inactive ions in the collector. The figures-of-merit of noise corner frequency (fc) to cutoff frequency ratio (fT), fC/f T, indicates that the SiGe HBT without SIC has a better low-frequency noise property for circuit application prior to the fT roll-off. Furthermore, at the onset of high injection effect, the conspicuous degradation of high-frequency properties also deteriorates the fCfT ratio of SiGe HBT without SIC.

Original languageEnglish
Pages (from-to)5729-5733
Number of pages5
JournalJapanese Journal of Applied Physics
Issue number9 A
StatePublished - 7 Sep 2007


  • Fluctuation noise
  • Impurity
  • Low-frequency noise
  • Selectively implanted collector


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